Aging does not impair the anabolic response to a protein-rich meal

Abstract

Background: Sarcopenia is a debilitating condition afflicting the elderly that may be facilitated by insufficient or ineffectual intake of dietary protein. We previously showed that free-form essential amino acids acutely stimulate muscle protein synthesis in both the young and the elderly. However, the ability of an actual protein-rich food to stimulate anabolism in the young and the elderly has not been explored. Objective: We aimed to characterize changes in plasma amino acid concentrations and to quantify muscle protein synthesis in healthy young (41 Ȁ 8 y old; n ҃ 10) and elderly (70 Ȁ 5 y old; n ҃ 10) persons after ingestion of a 113-g (4-oz) serving of lean beef. Design: Venous blood samples and vastus lateralis muscle biopsy samples were obtained during a primed (2.0 mol/kg) constant infusion (0.08 mol⅐kg Ҁ1 ⅐min Ҁ1 ) of L-[ring-13 C 6 ] phenylalanine. Plasma amino acid concentrations were measured and a mixedmuscle fractional synthesis rate (FSR) was calculated during the premeal period and for 5 h after beef ingestion. Results: Mixed-muscle FSR increased by Ȃ51% in both the elderly (mean Ȁ SE measurements: 0.072 Ȁ 0.004%/h and 0.108 Ȁ 0.006%/h before and after the meal, respectively) and the young (0.074 Ȁ 0.005%/h and 0.113 Ȁ 0.005%/h before and after the meal, respectively) after beef ingestion (P 0.001). Plasma amino acid concentrations peaked at Ȃ100 min after beef ingestion in both age groups but were substantially higher in the elderly (2185 Ȁ 134 nmol/mL compared with 1403 Ȁ 96 nmol/mL; P 0.001). Conclusion: Despite differences in the concentration of amino acids in the plasma precursor pool, aging does not impair the ability to acutely synthesize muscle protein after ingestion of a common protein-rich food.Am J Clin Nutr 2007;86:451-6.

The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men

“…However, data on this topic are equivocal, and there are various reasons to suggest that anabolic resistance is not a characteristic of aging per se (Burd et al 2012a, b). Data from our lab Pennings et al 2011b) as well others (Paddon-Jones et al 2004;Symons et al 2007Symons et al , 2011) have failed to detect any age-related differences in the post-prandial muscle protein synthetic response to dietary protein ingestion. A classic work by Volpi et al (2000) indicates that the proposed age-related blunting of the post-prandial muscle protein synthetic response to food intake may be more pronounced under conditions where both amino acids and carbohydrates are administered.…”

“…Clearly, age does not necessarily impair the capacity to direct ingested protein towards muscle protein synthesis. Using this approach, we extend on a previous work from our lab Pennings et al 2011b) as well as from other labs (Paddon-Jones et al 2004;Symons et al 2007Symons et al , 2011Chevalier et al 2011), further supporting the concept that anabolic resistance is not a characteristic of aging per se (Burd et al 2012a). We speculate that impairments in the post-prandial muscle protein synthetic response are likely more evident in more compromised, frail, and sedentary elderly populations, especially during short periods of hospitalization, bed rest, and/or immobilization Tieland et al 2012;Burd et al 2012a), as opposed to the healthy, independently living elderly included in the present study.…”

“…This blunted post-prandial muscle protein synthetic response is now generally thought to represent a key factor responsible for the age-related decline in skeletal muscle mass. However, there is an ongoing debate about the existence and extent of anabolic resistance in a healthy elderly population (Burd et al 2012a, b), since various studies have failed to confirm the presence of anabolic resistance in a physiological setting where post-prandial muscle protein synthesis rates were assessed following ingestion of a single meal-like bolus of protein Paddon-Jones et al 2004;Pennings et al 2011b;Symons et al 2007Symons et al , 2011.…”

Amino acid metabolism and regulatory effects in aging

“…There is clear evidence that increased amino acid or protein availability can enhance muscle protein synthesis and anabolism in young and older subjects [19][20][21]22 • ]. It has, however, been suggested that the recommended dietary allowance for protein (0.8 g/kg/day) may not be sufficient for older adults to maintain their muscle mass.…”

A sarcopenia prevalenciája, valamint az egészség- és életmódbeli tényezőkkel való kapcsolata a tartós ellátást nyújtó intézményekben élő idősek körében

“…Ez az elágazó láncú esszenciális aminosav aktiválja mind az inzulinfüggő, mind pedig az inzulintól független jelátviteli utat a fehérjeszintézis folyamatában, ezzel támogatva az izom-hipertrófia folyamatát [37]. A kezdeti laboratóriumi vizsgálatok, majd a humán kutatások arra is rámutatnak, hogy a bevitt fehér-jemennyiség napi eloszlása is szerepet játszik [38,39]. Minden főétkezésre ajánlott 20-30 grammos magas minőségű fehérjét biztosítani, vagyis a reggeli, az ebéd és a vacsora proteintartalma is közel azonos legyen.…”