NUTRITION-PROTEIN-MUSCLE PROTEIN SYNTHESIS-AGING


DEFINING ANABOLIC RESISTANCE – Implications for delivery of clinical care nutrition – 2018


Morton, Phillips et al
RECENT FINDINGS
1. Anabolic resistance is responsible, in part, for skeletal muscle atrophy with aging, muscle disuse, and during disease states
2. Anabolic resistance describes the reduced stimulation of muscle protein synthesis to a given dose of protein/amino acids and contributes to declines in skeletal muscle mass
3. Physical inactivity induces: anabolic resistance (that is likely exacerbated with aging), insulin resistance, systemic inflammation, decreased satellite cell content, and decreased capillary density
3. Critical illness results in rapid skeletal muscle atrophy that is a result of both anabolic resistance and enhanced skeletal muscle breakdown.
SUMMARY
1. Insofar as atrophic loss of skeletal muscle mass is concerned, anabolic resistance is a principal determinant of age-induced losses and appears to be a contributor to critical illness-induced skeletal muscle atrophy
2. Older individuals should perform exercise using both heavy and light loads 3x/wk, ingest at least 1.2 g of protein/kg/day, evenly distribute their meals into protein boluses of 0.40 g/kg, and consume protein within 2 h of retiring for sleep
3. During critical care, early, frequent, and multimodal physical therapies in combination with early, enteral, hypocaloric energy (∼10-15 kcal/kg/day), and high-protein (>1.2 g/kg/day) provision is recommended.

FAST DIGESTIVE PROTEINS AND SARCOPENIA OF AGING – 2017


Boirie, Yvesa; Guillet, Christelle
PURPOSE OF REVIEW
– The speed of dietary protein digestion influences post-meal amino acid availability which is crucial for improving altered anabolic response of skeletal muscle
– This is one feature of Sarcopenia during aging
RECENT FINDINGS
– Proteins can be classified as ‘fast’ or ‘slow’ proteins which can influence amino acids availability and their subsequent metabolic actions
– ‘Fast’ digestive proteins stimulate muscle protein synthesis and improve muscle function in several recent studies involving older patients
SUMMARY
– Using fast digestive proteins is of major interest to overcome ‘anabolic resistance’ of aging for limiting sarcopenia
– Fast proteins’ action on muscle anabolism may be stimulated by other nutrients like vitamin D or omega 3 fatty acids or by combination with exercise


HIGHER PROTEIN ASSOCIATED WITH LOWER FRAILTY IN OLDER ADULTS – 2016


Rahi B1, Feart C3. et al
METHODS
– Participants were community-dwelling older adults aged 65 and over
– Frailty was defined as a score of 3/5 among weight loss, exhaustion, muscle weakness, slowness, and physical activity
– Protein daily intake: ≥1 g/kg body weight
– Optimal energy intake defined as a daily intake ≥30 kcal/kg
CONCLUSIONS
– A 1 g/kg protein intake was associated with a lower prevalence of frailty in French community-dwelling older subjects


AGING IS ACCOMPANIED BY A BLUNTED MUSCLE PROTEIN SYNTHETIC RESPONSE TO PROTEIN – 2015


Benjamin Wall, Luc J. C. van Loon et al
PURPOSE
(1) Is impaired capacity to increase muscle PRO synthesis in response to protein intake a key contributor to sarcopenia?
(2) Do differences in post-absorptive and/or post-prandial muscle protein synthesis rates exist b/n healthy young and older men
PROCEDURES
(a) Comparing in post-absorptive muscle protein synthesis rates b/n 34 healthy young (22±1 y) and 72 older (75±1 y) men
(b) Comparing post-meal muscle protein synthesis rates between 35 healthy young (22±1 y) and 40 older (74±1 y) men
FINDINGS
(3) Muscle protein synthesis rates were >3 fold more responsive to dietary protein ingestion in the young
CONCLUSIONS
– Aging is associated with muscle anabolic inflexibility which represents a key physiological mechanism underpinning sarcopenia


EFFECT OF AGE ON MUSCLE PROTEIN SYNTHESIS – 2015


Markofski MM1, Volpi E8. et al
AIM
– Determine if age and sex differentially impact basal muscle protein synthesis and mTORC1 signaling
DESIGN
(1) 215 healthy, non-obese young (18-40y; 74 men, 52 women) and older (60-87y; 57 men, 32 women) adults
CONCLUSIONS
(1) Age and sex do not influence basal muscle protein synthesis
(2) However, basal mTORC1 in the elderly may contribute to insulin resistance and age-related anabolic resistance of skeletal muscle protein metabolism to nutrition and exercise


KEEPING OLDER MUSCLE YOUNG THROUGH PROTEIN & PHYSICAL ACTIVITY – 2014


Daniel R. Moore – Faculty of Kinesiology and Physical Education, University of Toronto
DIETARY PROTEIN
(1) Blunted muscle protein synthetic response to dietary protein, commonly referred to as “anabolic resistance,” is a major underlying cause of the loss of muscle with age
(2) Dietary strategies to overcome this decreased dietary amino acid sensitivity include:
– the ingestion of leucine enriched, rapidly digested proteins
– and/or greater protein ingestion in each main meal to maximally stimulate muscle anabolism
(3) Anabolic resistance is also a hallmark of a sedentary lifestyle at any age
EXERCISE
– Acute bouts of activity can restore the sensitivity of older muscle to dietary protein
– Provided physical activity is incorporated into the daily routine, muscle in older adults should retain its capacity for a robust anabolic response to protein comparable to younger peers
– Through its ability to “make nutrition better,” physical activity should be viewed as a vital component to maintaining muscle mass and function with age


BRANCHED AMINO ACIDS ARE ASSOCIATED WITH MUSCLE MASS IN OLDER ADULTS – 2014


Lustgarten MS1, Price LL2, Chale A1, Phillips EM1, Fielding RA3
BACKGROUND:
– Metabolic profiling may provide insight into biologic mechanisms related to muscle and fat-free mass in functionally limited older adults
CONCLUSIONS:
– Multiple BCAAs are markers of muscle CSA Cross-Sectional Area or the FFMI Fat-Free Mass Index in functionally limited older adults


INTERVENTIONS FOR SARCOPENIA IN AGING ADULTS – 2014


Cruz-Jentoft AJ1, Cederholm T
METHODS
– Studies investigating muscle mass plus strength or function outcome measures in populations of adults aged ≥50 years were selected
RESULTS
– Moderate quality evidence suggests that exercise interventions improve muscle strength and physical performance
– Essential amino acid (EAA) supplements, including ∼2.5 g of leucine, and HMB, show some effects in improving muscle mass and function parameters
CONCLUSION
– Supervised resistance exercise is recommended for individuals with sarcopenia


INTERACTIONS BETWEEN EXERCISE & NUTRITION TO PREVENT MUSCLE WASTING – 2012


Leigh Breen, Stuart M Phillips
MUSCLE ATROPHY
– Prolonged periods of net -ve muscle PRO balance, brought about by imbalance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB)
RESISTANCE TRAINING AND PROTEIN INTAKE
– Resistance exercise-induced rates of MPS and hypertrophy appear to be dependent on exercise volume (to achieve maximal muscle fibre recruitment), as opposed to the absolute load that is lifted


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