After short-term immobilization due to e.g. limb-injuries, bed-ridden periods during disease or e.g. hospitalization, sedentary lifestyle or just advancing age recovery of the skeletal muscle mass is crucial to return to, maintain or improve daily functional capability.

The research focus of the Protein Turnover group is to understand how protein turnover rates in the skeletal muscle is regulated and to explore the relative fluctuations in the underlying kinetics –protein synthesis and degradation rates – as being determinants for the net change in muscle protein mass under catabolic or anabolic conditions.

The two primary interventions are ingestion of protein and muscular contractions.

With the purpose to investigate how amino acids (or alike components) are 1) sensed, 2) affect intramuscular signaling, 3) stimulate muscle protein turnover rates, and 4) lead to changes in protein mass, the temporal and quantitative appearance of hyperaminoacidemia obtained by intake of intact or hydrolyzed proteins of different origin is applied in various experimental settings. The interaction of hyperaminoacidemia with (or in absence of) contractile activity is also investigated by performing interventions with muscle resistance exercises at various intensities or immobilization in combination with various protein feeding regimens.

Human in vivo designs are the preferred experimental model. Controlled experiments are challenged with applied settings to combine mechanistic and explorative methodologies linking acute molecular responses to longitudinal phenotypic changes. When advantageous for the research questions also animal models are used.

The vision of the science conducted by the Protein Turnover group is to contribute with evidence to formulate strategies for protein intake and/or muscular training for humans with the need to recover muscle mass.

Protein Turnover covers the two kinetic processes namely protein synthesis and breakdown that determines the net protein balance and thus whether proteins are accreted or lost. Therefore, for us the main tool is to measure the synthesis and breakdown rates of proteins in various tissues of interest. The kinetic rates are measured by tracing stable isotopically labeled amino acids. Our primary analytical tool is therefore mass spectrometry, which we use to trace and quantify labeled amino acids in obtained biological samples.

Methodologies: Skeletal muscle (vastus lateralis, trapezius, soleus), tendon (achilles and patella), as well as skin biopsies, interstitial fluid, and blood are collected and analyzed with various techniques, such as: embedded and sliced for histo- and immunochemistry, western blotting, reverse transcriptase polymerase chain reaction, and various both liquid chromatograph and gas chromatograph mass spectrometry applications. Further, with the purpose either to characterize or to assess longitudinal changes in body composition and functional performance, we have access to various scan types; magnetic resonance imaging, ultra sonic, and dual x-ray absorptiometry; as well as to a wide range of strength and functional assessment tools.


Group members:
Ass. professor Lars Holm, Professor Satoshi Fujita, Post doc Søren Reitelseder, Post doc Jakob Agergaard, PhD-student MD Jacob Bülow, PhD-student, MSc Grith W. Højfeldt, Scientific assistant, MSc, Kenneth H. Mertz, Scientific assistant, MSc-student Mikkel Jensen, Scientific assistant, MSc-student Jonas Lindberg, Academic employee Diana Lyng Christensen and several students at master and bachelor level.