La co-ingestione di leucina aumenta la sintesi proteica muscolare a seguito dell'ingestione di 15 g di proteine dopo l'esercizio contro resistenza negli uomini anziani

A.M. Holwerda, K.J.M. Paulussen, M. Overkamp, J.P.B. Goessens, I.F. Kramer, W.K.W.H. Wodzig, L.B. Verdijk, L.C.P.G.M. de Groo, L.J.C. van Loon

Am J Physiol Endocrinol Metab. 2019 May 21. doi: 10.1152/ajpendo.00073.2019. [Epub ahead of print]

Older adults have shown an attenuated post-exercise increase in muscle protein synthesis rates following ingestion of smaller amounts of protein when compared to younger adults. Consequently, it has been suggested that older adults require the ingestion of more protein to increase post-exercise muscle protein synthesis rates when compared to younger adults.

We investigated whether co-ingestion of 1.5 g free leucine with a single, 15 g bolus of protein further augments the post-prandial muscle protein synthetic response during recovery from resistance-type exercise in older men.

Twenty-four healthy older men (67±1 y) were randomly assigned to ingest 15 g milk protein concentrate (MPC80) with (15G+LEU; n=12) or without (15G; n=12) 1.5 g free leucine after performing a single bout of resistance-type exercise. Post-prandial protein digestion and amino acid absorption kinetics, whole-body protein metabolism, and post-prandial myofibrillar protein synthesis rates were assessed using primed, continuous infusions with L-[ring-2H5]-phenylalanine, L-[ring-2H2]-tyrosine and L-[1-13C]-leucine combined with the ingestion of intrinsically L-[1-13C]-phenylalanine labeled milk protein.

A total of 70±1% (10.5±0.2 g) and 75±2% (11.2±0.3 g) of the protein-derived amino acids were released in the circulation during the 6 h post-exercise recovery phase in 15G+LEU and 15G, respectively (P<0.05). Post-exercise myofibrillar protein synthesis rates were 16% (0.058±0.003 vs 0.049±0.002% h-1; P<0.05; based upon L-[ring-2H5]-phenylalanine) and 19% (0.071±0.003 vs 0.060±0.003% h-1,P<0.05; based upon L-[1-13C]-leucine) greater in 15G+LEU when compared with 15G.

Comment:  Leucine co-ingestion further augments the post-exercise muscle protein synthetic response to the ingestion of a single 15 g bolus of protein in older men.