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Life in Space for Life on Earth, ESA, Triest, 2010;

Increased Homer 2a/b expression by Resistive Vibration Exercise (RVE) in unloaded human soleus (SOL) and vastus lateralis (VL) muscle biopsies

Year: 2010

Salanova M, Schiffl G, Gutsmann M, Belavý D, Felsenberg D, Furlan S, Bortoloso B, Volpe P, Blottner D
Center of Space Medicine Berlin (ZWMB), Neuromuscular Group, Charité Universitätsmedizin Berlin, GERMANY; Center of Muscle and Bone Research (ZMK), Charité Universitätsmedizin Berlin, GERMANY; Department of Biomedical Sciences, University of Padova, I


The molecular mechanisms of human skeletal muscle adaptation following prolonged disuse are still largely unknown. Recently, protein calcium sensors of the homer family (comprised of short and long isoforms) have been proposed to directly modulate the activity of various ion channels. In an attempt to further identify reliable molecular biomarkers of human skeletal muscle-disuse, we monitored changes of the homer molecular long isoforms in SOL and VL muscle biopsies following 60 days of voluntary bed rest 6° head down tilt (HDT) without and with two exercise countermeasures, one of which included resistive vibration exercise (RVE) that makes use of neuroreflexive stimulation of skeletal muscle with high contraction cycles using a modified Galileo-Space device (1).

Twenty-four healthy male subjects underwent 60-days of bed-rest HDT and were randomized to an inactive control group (CTR, n=9), a high-load resistive exercise group (RE, n=8), and a group that performed the same high-load resistive exercises but with the addition of whole-body vibration (RVE, n=7) (1). Muscle biopsy from SOL and VL were performed before and after HDT and the expression pattern of homer 2 specific isoforms was investigated at mRNA and protein level in combination with morphometric measurements of myofiber cross-sectional area (CSA), and myofibre type distribution (fast and slow myosin heavy chain), as indices of muscle atrophy and myofibre phenotype composition.

Preliminary results showed that: homer 2a/b expression was significantly decreased in human SOL (-15%, p<0.05) after HDT muscle inactivity in CTR group and such changes correlated well with changes in myofibre size and phenotype composition. In the RE group, no major changes were found. However, in the RVE group, homer 2a/b expression significantly increased in both SOL (20%, p<0.05) and VL (25%, p<0.01) muscle homogenates.

Our findings support the notion that homer 2a/b expression may be upregulated by neuroreflexive stimuli as highlighted by the RVE protocol. Therefore, RVE countermeasure appears to be very effective to support expression of neuronally induced muscle signaling protein expression that otherwise may be impaired following prolonged disuse-induced skeletal muscle atrophy or following exposure to microgravity in absence of reliable countermeasures.

Deutsches Zentrum fur Luft-und Raumfahrt (DLR), Germany (# 50WB0821 to D.B.)
(1) Belavy DL et al., JMNI 2010

Keywords: Galileo Space, Counter Measure, BBR 2
GID: 2296; Last update: 18.06.2010
More information: Original Article