Muscle Protein Turover
Conditions
Interventions
Three days of immobilization via a full leg cast
One leg will be immobilized at a 30 degree knee joint angle of flexion for 3
days by means of leg cast (see Figure 1). The leg to be immobilized will
Sponsors
Maastricht University
Eligibility
Age
18 Years to 99 Years
Inclusion criteria
Inclusion criteria: * Moderately active * Male or female age 18-35 or 60-80 years of age inclusive * BMI not lower than 18.5 and not higher than 30 kg/m2 * Having given informed consent
Exclusion criteria
Exclusion criteria: * Previous participation in a 13C amino acid tracer study (within the last 5 years) * Lower limb and/or back injuries * A history of thrombosis/cardiovascular disease * Use of anticoagulants * Musculoskeletal/orthopedic disorders * Structured resistance exercise training * Use of corticosteroids * Current use of protein supplements (during the study) * Diabetes (type I or II) * Pregnancy * Hormone replacement therapy * Third generation oral contraceptives * Use of tobacco products
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Main study parameter/endpoint The main study endpoint is cumulative FSR as a measure of muscle protein synthesis rates (MPS) based on the oral tracer deuterium oxide. In order to determine cumulative FSR, the following parameters will be measured via GC-C-IRMS and GCMS respectively: * Muscle protein-bound L-[2,3,3,3-2H4]-alanine enrichment (expressed as MPE) * Plasma free L-[2,3,3,3-2H4]-alanine enrichment (expressed as MPE) * Saliva 2H2O enrichment (Expressed as APE) | — |
Secondary
| Measure | Time frame |
|---|---|
| Secondary study parameters/endpoints Secondary endpoints include: * Quadriceps whole-muscle CSA as assessed via CT scan. * Plasma, muscle free, and muscle protein-bound L-[ring-13C6]-phenylalanine enrichment. * Fractional breakdown rates (FBR) of muscle protein based on 3,3-D2 phenylalanine tracer dilution in plasma and muscle. * Fractional synthesis rates (FSR) of muscle protein based on L-[ring-13C6]-phenylalanine tracer incorporation into bound muscle protein. * Activation of signaling molecules regulating muscle protein synthesis and breakdown (specified in 8.3.6.5) will be established via Western blots. Quantitative Real-Time PCR Analysis of MAFbx/Atrogin-1, MuRF1, FoxO and Ubiquitin Expression will also be performed. | — |
Countries
Netherlands
Outcome results
None listed