The regulatory mechanisms behind muscle-mass gains and losses were investigated in a large clinical trial. State-of-the-art research techniques (arterio-venous balances, stable-isotopes infusion, intrinsically-labelled protein, hyperinsulinemic euglycemic clamp, blood-flow measurements) were applied in young and elderly individuals to gain insight into the role of insulin in postprandial muscle-protein metabolism.
Although it is well known that dietary protein is essential for building and preserving muscle mass, the impact of the other macronutrients on muscle-mass gains and losses remains to be established. A series of mechanistic studies was completed to assess the impact of the macronutrient composition of a meal on the post-prandial muscle-protein synthetic response. These studies provide an answer to the question of whether the addition of carbohydrate (1st study) and fat (2nd study), to a protein-rich meal, modulates post-prandial muscle-protein metabolism. The third study investigates the effect of a habitual high-protein diet compared with normal-protein diet on digestion and absorption kinetics and the subsequent muscle-protein synthetic response to dietary-protein ingestion. A longer-term randomised controlled trial was performed in parallel, to determine whether a high-protein diet can effectively preserve muscle mass during energy-intake restriction.
Another work package investigated the impact of the macronutrient composition of a nutritional supplement on postprandial skeletal-muscle-protein synthesis in the elderly. Analyses have been performed and papers are currently being written. In addition, a follow-up study evaluated the course of pre-existing muscle-fibre atrophy, in elderly females with fall-related hip fracture, during hospital admission and the impact of a nutritional supplement (Pro-Hip).
It has been speculated that factors other than ageing might contribute to the loss of muscle mass in older individuals. Therefore, a work package, with acute human intervention trials, was initiated to investigate the role of gender, physical inactivity and obesity in relation to muscle-mass preservation.
|Scientific papers in peer-reviewed journals||2015 Post-prandial muscle protein synthesis: "You are what you just ate"||View summary|
|Posters||2015 There are no nonresponders to resistance-type exercise training in older men and women||View summary|
|Scientific papers in peer-reviewed journals||2015 Impact of the Macronutrient Composition of a Nutritional Supplement on Muscle Protein Synthesis Rates in Older Men: A Randomized, Double Blind, Controlled Trial||View summary|
|Scientific papers in peer-reviewed journals||2015 Short-term muscle disuse lowers myofibrillar protein synthesis rates and induces anabolic resistance to protein ingestion||View summary|