HEALTH-2007-2.4.5-10: Understanding and combating age related muscle weakness
*MYOAGE*

Sarcopenia is a universal, age-related loss of muscle mass associated with a
loss of strength and function resulting in muscle weakness. It often leads to
progressive disability and loss of independence (Lauretani et al. 2003). The
development of sarcopenia has also been associated with increased morbidity and
mortality (Rantanen et al. 2003, Ling et al. 2010). The onset and dimension of
the age related decrease in muscle mass and strength are muscle dependent and
heterogeneous and it can occur as early as 30 years of age and results in a
loss of about 30-50% of the muscle mass by the age of 80 years (Evans et al.
1997; Beenakker et al. submitted).
Despite its clinical importance, the pathophysiology leading to sarcopenia is
not well understood. Environmental factors, such as a sedentary life style and
malnutrition contribute to sarcopenia; other possible causes of sarcopenia
include systemic changes such as a decreased growth hormone production and
increased inflammatory cytokine secretion (Morley et al. 2001).
On the cellular level, the age associated decline in muscle mass and function
results from the loss of muscle fibers, especially the type II fibers (Lexell
et al. 1995), as well as a loss of the cross-sectional area of remaining fibers
(Vandervoort et al. 2002). The number of sublaminar (CD 34+) satellite cells,
the muscle fiber progenitor cells capable of self renewal and sufficient for
postnatal muscle growth and repair, and the proliferative capacity of these
cells is inversely related with chronological age (Renault et al. 2000; Sajko
et al. 2004; Widmer et al. 1995). Additional factors related to the decline in
muscle mass is a lower supply of nutrients through diminished vascularisation
and arteriosclerosis as well as a decreased efficiency of metabolism of the
nutrients and muscle changes due to chronic inflammation. Epidemiological
studies have shown a correlation between high levels of inflammatory cytokines
(TNF-α and IL-6), a low level of IGF-1, high levels of oxidative stress,
decreased mitochondrial function and sarcopenia. Recently, our group was able
to show that a high innate production capacity of TNF-α preceded a steeper
decline in muscle strength over time within a population-based prospective
follow up study (Taekema et al. 2007). However, in this study the underlying
cellular and molecular mechanisms cannot be identified.

The aim of the represent proposal is twofold,
1. [PHASE 1] the establishment of a human tissue biobank including muscle and
blood, and additionally from a subset subset of subjects fat and skin biopsies
will be taken. Samples will be distributed throughout the consortium Myoage (1)
for the optimisation of all protocols to be able to translate basic biological
data obtained with model organisms/systems to human material, (2) the
understanding of the various biological mechanisms involved in sarcopenia, (3)
intraindividual mechanisms related to human ageing, studied in different types
of human tissues.
2. [PHASE 2] studying the contribution of quantity, quality and control of
muscle make to loss of mobility and quality of life in an elderly population
being highly and less active, together with a control group. A total of 525
subjects will be recruited in five European centers (each recruitment center
105 subjects in total, 35 subjects in each group). Leiden is one of the
recruitment centers. Subjects will be phenotype on functional, imaging and
cellular level. All recruitment centers use the same protocols / measurements.

PHASE 1.1.
Observational, cross sectional study. Inclusion of 55 patients undergoing knee
replacement and 105 patients undergoing hip replacement either because of a
primary locomotor disease or
PHASE 1.2.
Observational, cross sectional study. Inclusion of 20 patients undergoing knee
replacement
PHASE 2:
Observational, cross sectional study. Inclusion of 105 healthy subjects,
divided over three groups: healthy young, sedentary old, active old.

PHASE 1:
Patients are under general anesthesia and undergoing hip or knee surgery.
Muscle tissue samples are taken from the distal part or proximal part of m.
vastus lateralis, which will be within the operation area. Blood will taken
during the operation. Additional fat and skin biopsies will be taken from the
operation area. No additional risk or burden is involved.
PHASE 2:
Subjects are invited to the LUMC to perform a number of tests, clustered over
two days. The tests include maximal performance, i.e. lung function, 6 meter
walk test and maximal quadriceps strength. The maximal performance tests are
spread over two days. The order of the test battery is such that physically and
mentally strenuous tasks are separated by passive tasks. The test battery
includes one invasive procedure, i.e. the needle biopsy.
1) Quadriceps dynamometry is performed in an isometric testing chair in which
the subject is positioned upright. The test is isometrically, i.e. static
performance without any moving (parts). The electrical equipment of the chair
consists of a low voltage force transducer. The maximal force tasks may result
in some muscle soreness which may last for one or two days.
2) Electrical stimulation is performed using commercially available
stimulating devices which meet all required certifications. Muscle stimulation
is performed at a low intensity (max 50% of MVC output). EMG-NMS is
non-invasive and does not have side effects.
3) Haptic robotics. A commercially available robot manipulator is being used,
meeting CE certification. Electrical parts are yielded from the subject. An
isolation transformer is applied. The machine is safeguarded against unwanted
displacements both by software and hardware boundaries.
4) Spirometry is a routine lung function assessment bearing no risks or side
effects
5) The needle biopsy is performed using hollow needle, thickness 3 mm which is
4cm inserted into the m. vastus lateralis muscle. The burden of the procedure
is comparable to a widely applied procedure as taking skin biopsies. Before
biopsy, the skin is cleaned and anesthetics are applied. The rate of bleeding
after taking the biopsy and infection is neglectable. Some but not all
patients, experience some pain at the moment the biopsy is taken (like
myalgia). Sometimes a small haematoma will develop, although in our 3 previous
studies (Jazet IM et al 2008; Jazet IM et al, 2005; Hammer et al, 2008) none
of the patients developed this. Furthermore the patient might experience a
heavy feeling in the involved muscle the next 24-48 hours. The procedure is
applied by an experienced medical physician.
6) Ultrasound is applied by fully certified equipment. No risks are involved.
7) DEXA scan applied by fully certified equipment. No risks are involved.
8) Force plate: the force plate on which subjects stand to assess balance and
perform the vertical jumps is integrated in a platform of sufficient size (1
square meter approximately) to prevent subjects from falling off.
9) MRI scan is applied by fully certified equipment. No risks are involved.
10) Insertion of an IV needle is performed by experienced and qualified
personnel. The IV needle will remain in situ for about 2,5 hours (time to
complete OGTT test). Risks of this (routine) procedure are minimal.