Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content - PubMed (original) (raw)

Randomized Controlled Trial

Whey protein ingestion in elderly persons results in greater muscle protein accrual than ingestion of its constituent essential amino acid content

Christos S Katsanos et al. Nutr Res. 2008 Oct.

Abstract

It is recognized that both whey protein (WY) and essential amino acids (EAA) are stimuli for muscle protein anabolism. The aim of the present study was to determine if the effects of WY ingestion on muscle protein accrual in elderly persons are due solely to its constituent EAA content. Fifteen elderly persons were randomly assigned to ingest a bolus of either 15 g of WY, 6.72 g of EAA, or 7.57 g of nonessential amino acids (NEAA). We used the leg arteriovenous model to measure the leg phenylalanine balance, which is an index of muscle protein accrual. Phenylalanine balance (nmol x min(-1) kg lean leg mass(-1)) during the 3.5 hours after the bolus ingestion improved in the WY (-216 +/- 14 vs -105 +/- 19; P < .05) but not in the EAA (-203 +/- 21 vs -172 +/- 38; P > .05) or NEAA groups (-203 +/- 19 vs -204 +/- 21; P > .05). The insulin response (uIU x mL(-1) 210 min(-1)) during the same period was lower in both the NEAA (48 +/- 40) and EAA (213 +/- 127) when compared to the WY (1073 +/- 229; P < .05). In conclusion, WY ingestion improves skeletal muscle protein accrual through mechanisms that are beyond those attributed to its EAA content. This finding may have practical implications for the formulation of nutritional supplements to enhance muscle anabolism in older individuals.

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Figures

Fig. 1

Fig. 1

Diagram of the blood and muscle sampling protocol. Data were collected before and after ingestion (at time 0) of 15 g of whey protein, 6.72 g of essential amino acids (EAA), or 7.57 g of non-essential amino acids (NEAA). The EAA and NEAA mixtures contain the EAA and NEAA, respectively, found in the 15 g of the whey protein. Leg arterio-venous blood samples were taken at several times before and every 15 minutes following the ingestion of either whey protein or amino acid mixtures for the determination of the leg blood phenylalanine balance. Blood flow was determined before and following ingestion of the three mixtures and by using indocyanine green (ICG) dye infusion in the femoral artery. A leg muscle biopsy was performed at the end of the sampling protocol to determine changes in the muscle free phenylalanine concentration compared to the period prior to the ingestion of the whey protein or amino acids mixtures.

Fig. 2

Fig. 2

Blood phenylalanine concentration in the femoral artery in the postabsorptive period (average value) and during a 210-minute period following the ingestion of either whey protein or one of the amino acid (either essential or non-essential) mixtures. n=5 for each group. Values are presented as means ± SEM.

Fig. 3

Fig. 3

Plasma insulin concentration in the femoral artery in the postabsorptive period (average value) and during a 210-minute period following the ingestion of either whey protein or one of the amino acid (either essential or non-essential) mixtures. n=5 for each group. Values are presented as means ± SEM. *Values over time within each group are significantly different from postabsorptive by ANOVA coupled with Dunnett’s post-hoc multiple comparisons tests at P < .05.

Fig. 4

Fig. 4

Blood phenylalanine balance in the leg in the postabsorptive period (average value) and during a 210-minute period following the ingestion of either whey protein or one of the amino acid (either essential or non-essential) mixtures. n=5 for each group. Values are presented as means ± SEM.

Fig. 5

Fig. 5

Average responses for the leg blood phenylalanine balance in the postabsorptive period and during a 210-minute period following the ingestion (postprandial) of either whey protein or one of the amino acid (either essential or non-essential) mixtures. n=5 for each group. Values are presented as means ± SEM. *Values between postabsorptive and postprandial responses within group are significantly different by paired-samples t test at P < .05.

Fig. 6

Fig. 6

Change in the leg blood phenylalanine balance (difference between the average postprandial period value and the corresponding postabsorptive period value) as a result of the ingestion of either whey protein or one of the amino acid (either essential or non-essential) mixtures. n=5 for each group. Values are presented as means ± SEM. *Values are significantly different from the whey protein group by ANOVA coupled with Dunnett’s post-hoc multiple comparisons tests at P < .05.

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