Anabolic properties of BCKA and BCAA in vivo
in older men

Protein and/or essential amino acids are important for stimulating muscle protein synthesis (MPS) rates and inhibiting muscle protein breakdown. The anabolic properties to protein feeding can be increased by the co-ingestion of free leucine, thereby increasing the amount of dietary protein derived amino acids that are used for de novo muscle protein synthesis. Consequently branched chain amino acid (BCAA) supplementation or fortification can be used to increase MPS. However, supplementing with high amounts of protein and/or BCAA, necessary to stimulate MPS, can be harmful for patients suffering from for example Chronic Kidney Disease (CKD). Supplementation with branched chain keto acids (BCKA) may be of particular relevance in these conditions as these keto analogues do not provide nitrogen (N) and may help to reduce metabolic workload of liver and kidneys. However, it remains to be established whether BCAA and BCKA can be useful in stimulating MPS in vivo in humans.

- We hypothesize that ingestion of BCAA will increase post-prandial plasma amino acid availability, thereby increasing myofibrillar muscle protein synthesis rates above basal
values.

- We hypothesize that ingestion of BCKA will increase post-prandial plasma amino acid availability, thereby increasing myofibrillar muscle protein synthesis rates above basal
values.

- We hypothesize that BCAA and BCKA is equally or less effective in increasing post-prandial plasma amino acid availability and myofibrillar muscle protein synthesis rates when compared to milk protein.

Muscle biopsies will be taken at timepoints: 0h, 2h and 5h after ingestion of the beverage.

A beverage (300 mL) containing 6 g of BCAA, 6 g of BCKA- or 30 g of milk protein will be consumed.