Assessing Muscle Protein Synthesis Rates In Vivo in Humans: The Deuterated Water (HO) Method.

Skeletal muscle tissue is in a constant state of turnover, with muscle tissue protein synthesis and breakdown rates ranging between 1% and 2% across the day in vivo in humans. Muscle tissue remodeling is largely controlled by the up- and down-regulation of muscle tissue protein synthesis rates. Research studies generally apply stable isotope-labeled amino acids to assess muscle protein synthesis rates in vivo in humans.

Access to a pre-sleep protein snack increases daily energy and protein intake in surgical hospitalized patients.

Background & Aim: In hospitalized patients, daily protein intake remains far below WHO requirements for healthy adults (0.8 g·kg·d) as well as ESPEN guidelines for patients (1.2-1.

The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans.

The belief that the anabolic response to feeding during postexercise recovery is transient and has an upper limit and that excess amino acids are being oxidized lacks scientific proof. Using a comprehensive quadruple isotope tracer feeding-infusion approach, we show that the ingestion of 100 g protein results in a greater and more prolonged (>12 h) anabolic response when compared to the ingestion of 25 g protein. We demonstrate a dose-response increase in dietary-protein-derived plasma amino acid availability and subsequent incorporation into muscle protein.

Higher Muscle Protein Synthesis Rates Following Ingestion of an Omnivorous Meal Compared with an Isocaloric and Isonitrogenous Vegan Meal in Healthy, Older Adults.

Background: Plant-derived proteins are considered to have fewer anabolic properties when compared with animal-derived proteins. The anabolic properties of isolated proteins do not necessarily reflect the anabolic response to the ingestion of whole foods. The presence or absence of the various components that constitute the whole-food matrix can strongly impact protein digestion and amino acid absorption and, as such, modulate postprandial muscle protein synthesis rates.

Trabecular, but not cortical, bone tissue protein synthesis rates are lower in the femoral head when compared to the proximal femur following an intracapsular hip fracture.

Background: All musculoskeletal tissues are in a constant state of turnover, with a dynamic equilibrium between tissue protein synthesis and breakdown rates. The synthesis of protein allows musculoskeletal tissues to heal following injury. Yet, impaired tissue healing is observed following certain injuries, such as geriatric hip fractures.

Branched-chain ketoacid co-ingestion with protein lowers amino acid oxidation during hemodialysis: A randomized controlled cross-over trial.

Background & Aims: Hemodialysis removes amino acids from the circulation, thereby stimulating muscle proteolysis. Protein ingestion during hemodialysis can compensate for amino acid removal but may also increase uremic toxin production. Branched-chain ketoacid (BCKA) co-ingestion may provide an additional anabolic stimulus without adding to uremic toxin accumulation.

Vicia faba Peptide Network Supplementation Does Not Differ From Milk Protein in Modulating Changes in Muscle Size During Short-Term Immobilization and Subsequent Remobilization, but Increases Muscle Protein Synthesis Rates During Remobilization in Healthy Young Men.

Background: Muscle mass and strength decrease during short periods of immobilization and slowly recover during remobilization. Recent artificial intelligence applications have identified peptides that appear to possess anabolic properties in in vitro assays and murine models.

Objectives: This study aimed to compare the impact of Vicia faba peptide network compared with milk protein supplementation on muscle mass and strength loss during limb immobilization and regain during remobilization.

Cheese Ingestion Increases Muscle Protein Synthesis Rates Both at Rest and During Recovery from Exercise in Healthy, Young Males: A Randomized Parallel-Group Trial.

Background: Protein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored.

Thigh muscles are more susceptible to age-related muscle loss when compared to lower leg and pelvic muscles.

Background: A key hallmark of aging is the progressive loss of skeletal muscle mass. Due to limitations of the various methods typically applied to assess muscle mass, only limited information is available on age-related differences between various muscle groups. This study assessed differences in individual lower body muscle group volumes between healthy young and older males.

Intradialytic Protein Ingestion and Exercise do Not Compromise Uremic Toxin Removal Throughout Hemodialysis.

Objective: Dietary protein and physical activity interventions are increasingly implemented during hemodialysis to support muscle maintenance in patients with end-stage renal disease (ESRD). Although muscle maintenance is important, adequate removal of uremic toxins throughout hemodialysis is the primary concern for patients. It remains to be established whether intradialytic protein ingestion and/or exercise modulate uremic toxin removal during hemodialysis.

Differential effects of leucine and leucine-enriched whey protein on skeletal muscle protein synthesis in aged mice.

Background & Aims: It has been suggested that anabolic resistance, or a blunted protein synthetic response to anabolic stimuli, contributes to the failure of muscle mass maintenance in older adults. The amino acid leucine is one of the most prominent food-related anabolic stimuli. However, data on muscle protein synthesis (MPS) after administration of a single bolus of leucine in aged populations is lacking and long-term single leucine supplementation has not been shown to increase muscle mass.

Protein Supplementation Augments Muscle Fiber Hypertrophy but Does Not Modulate Satellite Cell Content During Prolonged Resistance-Type Exercise Training in Frail Elderly.

Objective: Protein supplementation increases gains in lean body mass following prolonged resistance-type exercise training in frail older adults. We assessed whether the greater increase in lean body mass can be attributed to muscle fiber type specific hypertrophy with concomitant changes in satellite cell (SC) content.

Design: A total of 34 frail elderly individuals (77 ± 1 years, n = 12 male adults) participated in this randomized, double-blind, placebo-controlled trial with 2 arms in parallel.

Glycemic control during consecutive days with prolonged walking exercise in individuals with type 1 diabetes mellitus.

Aims: Despite its general benefits for health, exercise complicates the maintenance of stable blood glucose concentrations in individuals with type 1 diabetes. The aim of the current study was to examine changes in food intake, insulin administration, and 24-h glycemic control in response to consecutive days with prolonged walking exercise (∼8h daily) in individuals with type 1 diabetes.

Methods: Ten individuals with type 1 diabetes participating in the worlds' largest walking event were recruited for this observational study.

The Martin Vigorimeter Represents a Reliable and More Practical Tool Than the Jamar Dynamometer to Assess Handgrip Strength in the Geriatric Patient.

Background: Geriatric patients with low skeletal muscle mass and strength generally have a relatively poor clinical outcome following acute illness. Therefore, it is recommended to routinely assess skeletal muscle mass and strength in patients admitted to the acute care geriatric ward. Handgrip strength is generally measured as a proxy for muscle strength and/or functional performance.

Co-ingesting milk fat with micellar casein does not affect postprandial protein handling in healthy older men.

Background & Aim: Dietary protein digestion and absorption plays an important role in modulating postprandial muscle protein synthesis. The impact of co-ingesting other macronutrients with dietary protein on protein digestion and absorption and the subsequent muscle protein synthetic response remains largely unexplored. This study investigated the impact of co-ingesting milk fat with micellar casein on dietary protein-derived amino acid appearance in the circulation and the subsequent postprandial muscle protein synthetic response in healthy older men.

A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus.

Dietary nitrate (NO3(-)) supplementation has been proposed as an emerging treatment strategy for type 2 diabetes. We hypothesized that ingestion of a single bolus of dietary NO3(-) ingestion improves oral glucose tolerance in patients with type 2 diabetes. Seventeen men with type 2 diabetes (glycated hemoglobin, 7.

The muscle protein synthetic response to food ingestion.

Preservation of skeletal muscle mass is of great importance for maintaining both metabolic health and functional capacity. Muscle mass maintenance is regulated by the balance between muscle protein breakdown and synthesis rates. Both muscle protein breakdown and synthesis rates have been shown to be highly responsive to physical activity and food intake.

There Are No Nonresponders to Resistance-Type Exercise Training in Older Men and Women.

Objective: To assess the proposed prevalence of unresponsiveness of older men and women to augment lean body mass, muscle fiber size, muscle strength, and/or physical function following prolonged resistance-type exercise training.

Design/setting/participants: A retrospective analysis of the adaptive response to 12 (n = 110) and 24 (n = 85) weeks of supervised resistance-type exercise training in older (>65 years) men and women.

Measurements: Lean body mass (DXA), type I and type II muscle fiber size (biopsy), leg strength (1-RM on leg press and leg extension), and physical function (chair-rise time) were assessed at baseline, and after 12 and 24 weeks of resistance-type exercise training.

Short-term muscle disuse atrophy is not associated with increased intramuscular lipid deposition or a decline in the maximal activity of key mitochondrial enzymes in young and older males.

Aging is generally accompanied by a progressive loss of skeletal muscle mass and impairments in metabolic function. Even a few days of muscle disuse (such as that occurring during injury or illness) leads to considerable loss of muscle mass and strength. It has been speculated that short, successive periods of muscle disuse throughout the lifespan may be largely responsible for the age-related loss of muscle mass.