Meta AnalysisID 3096

评估亮氨酸触发与阈值假说：系统性与叙述性综述

CRD42021227295

1. What is the leucine threshold hypothesis? - a dose-response analysis between leucine content and postprandial muscle protein synthesis 2. What characteristics determine the leucine trigger hypothesis and cause the gr

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Meta Analysis Id: 3096
Evidence Id: 11654
Core Evidence Id: 11654
Source Meta Analysis Id: 3047
Herb2 Meta Analysis Id: HBMA003047
Crd Id: CRD42021227295
Title: Assessing the leucine trigger and threshold hypothesis: a systematic and narrative review
Review Question: 1. What is the leucine threshold hypothesis? - a dose-response analysis between leucine content and postprandial muscle protein synthesis 2. What characteristics determine the leucine trigger hypothesis and cause the greatest effect on postprandial muscle protein synthesis? a. Time to peak plasma leucine concentration b. Absolute plasma leucine concentration c. Total plasma leucine concentration 3. Is there a specific level of total and/or absolute concentration of plasma leucine, whereby a greater value would provide no further benefit on muscle protein synthesis?
Study Type Included: Randomized controlled trials
Condition Being Studied: Nutritional metabolism relating to muscle health has significant clinical implications and implications for population health (e.g. mitigating the development of sarcopenia) across the lifespan. Muscle protein synthesis is modulated through protein (predominately leucine) intake and muscle contractions, whilst a period of muscle disuse induces resistance to both stimuli, known as anabolic resistance. Anabolic resistance is a hallmark of numerous non-communicable diseases, and prevalent in the critical care setting, and muscle mass is a predictor of morbidity and mortality. As clinical nutritional and exercise interventions are becoming more popular in the treatment of such diseases (exercise as medicine) it is imperative that we understand more about the regulation of muscle mass maintenance. Thus, a better understanding of the muscle protein synthetic response to muscle contractions and protein (and leucine) intake permits the opportunity for the betterment of health. By clearly defining, quantifying, and testing the leucine trigger and threshold theory we will have a thorough understanding of muscle protein turnover and be able to provide more confident nutritional recommendations across populations such as older adults, patients, and all individuals who are likely to experience reduced anabolic sensitivity in muscle.
Participant: Healthy adults with no acute or chronic physical illnesses and of any exercise training status.
Animal
Human Disease Modelled
Intervention: The primary intervention to be reviewed is a single bolus of any protein source (subsequent analysis will distinguish between isolated sources, whole food sources, and co-ingestion or fortification with isolated amino acids) consumed in close proximity to a resistance exercise stimulus (+ or - 1 hour). Resistance exercise to be used as a stimulus for upregulating muscle protein synthesis. Plasma leucine concentrations must be collected in the postprandial post-exercise period. Additionally, the utilization of a staple isotope continuous infusion tracer protocol using the precursor-product equation (fractional synthesis rate or FSR) must be utilized, this will provide muscle protein synthetic response to the ingestion of different quantities of leucine within a single bolus of protein.
Comparator Control: A control group or a comparator group. The control or comparator group will consume another source of exogenous food.
Main Outcome: To measure the 3 main outcomes, only groups ingesting an isolated protein source will be utilized Inclusion criteria Isolated protein source (see below for definition) isolated protein source with the fortification of amino acids An isolated protein source can be defined as a protein source isolated from whole food and low in carbohydrates and fat. For example, whey protein isolated from milk. Main outcome 1 Leucine content (g) Fractional Synthetic Rate (FSR) (% per hour) Main outcome 2 Mixed muscle and/or myofibrillar protein synthesis measured as FSR during the post-exercise and post-prandial period The leucine trigger hypothesis is thought to be characterized by 3 factors: Time to peak plasma leucine concentration (minutes) Absolute plasma leucine concentration (micromoles/Litre) AUC or total plasma leucine concentration (micromoles/Litre) Main outcome 3 FSR (% per hour) Absolute plasma leucine concentration (micromoles/Litre) AUC plasma leucine concentration (micromoles/Litre) Groups that include the co-administration of other macronutrients with isolated protein, isolated amino acids, and whole foods will be included in a subgroup analysis Measures of effect Muscle protein synthesis (FSR % change from baseline) Time to peak plasma leucine concentration (minutes) Absolute plasma leucine concentration (% change from baseline) or (micromoles/Litre) AUC plasma leucine concentration (micromoles/Litre over FSR time frame)
Outcome Measure
Additional Outcome: None Measures of effect Not applicable
Study Method: Systematic review
Keyword: Diagnostic Tests, Routine; Humans; Leucine; Precipitating Factors
Contact: Christopher Koscien [email protected]
Organisational Affiliation: University of Exeter
Funding Source
Other Selection Criteria
Final Publication
Same Topic Review
Published Protocol
Review Type
Language: English
Country: England
Review Stage: Review Ongoing
First Submission Date: 2021-01-10
Registration Date: 2021-03-16
Anticipated Start Date: 2021-01-07
Anticipated Completion Date: 2021-11-01
Title Cn: 评估亮氨酸触发与阈值假说：系统性与叙述性综述
Title En: Assessing the leucine trigger and threshold hypothesis: a systematic and narrative review
Bilingual Status: complete