| 1. |
- Fluck, Martin, et al.
(författare)
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Early Changes in Costameric and Mitochondrial Protein Expression with Unloading Are Muscle Specific
- 2014
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Ingår i: BioMed Research International. - : Hindawi Limited. - 2314-6133 .- 2314-6141.
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesised that load-sensitive expression of costameric proteins, which hold the sarcomere in place and position the mitochondria, contributes to the early adaptations of antigravity muscle to unloading and would depend on muscle fibre composition and chymotrypsin activity of the proteasome. Biopsies were obtained from vastus lateralis (VL) and soleus (SOL) muscles of eight men before and after 3 days of unilateral lower limb suspension (ULLS) and subjected to fibre typing and measures for costameric (FAK and FRNK), mitochondrial (NDUFA9, SDHA, UQCRC1, UCP3, and ATP5A1), and MHCI protein and RNA content. Mean cross-sectional area (MCSA) of types I and II muscle fibres in VL and type I fibres in SOL demonstrated a trend for a reduction after ULLS (0.05 <= P < 0.10). FAK phosphorylation at tyrosine 397 showed a 20% reduction in VL muscle (P = 0.029). SOL muscle demonstrated a specific reduction in UCP3 content (-23%; P = 0.012). Muscle-specific effects of ULLS were identified for linear relationships between measured proteins, chymotrypsin activity and fibre MCSA. The molecular modifications in costamere turnover and energy homoeostasis identify that aspects of atrophy and fibre transformation are detectable at the protein level in weight-bearing muscles within 3 days of unloading.
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| 2. |
- Tesch, Per, et al.
(författare)
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Skeletal muscle proteolysis in response to short-term unloading in humans
- 2008
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 105:3, s. 902-906
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Tidskriftsartikel (refereegranskat)abstract
- Skeletal muscle atrophy is evident after muscle disuse, unloading,or spaceflight and results from decreased protein content asa consequence of decreased protein synthesis, increased proteinbreakdown or both. At this time, there are essentially no humandata describing proteolysis in skeletal muscle undergoing atrophyon Earth or in space, primarily due to lack of valid and accuratemethodology. This particular study aimed at assessing the effectsof short-term unloading on the muscle contractile proteolysisrate. Eight men were subjected to 72-h unilateral lower limbsuspension (ULLS) and intramuscular interstitial levels of thenaturally occurring proteolytic tracer 3-methylhistidine (3MH)were measured by means of microdialysis before and on completionof this intervention. The 3MH concentration following 72-h ULLS(2.01 ± 0.22 nmol/ml) was 44% higher (P < 0.05) thanbefore ULLS (1.56 ± 0.20 nmol/ml). The present experimentalmodel and the employed method determining 3MH in microdialysatespresent a promising tool for monitoring skeletal muscle proteolysisor metabolism of specific muscles during conditions resultingin atrophy caused by, e.g., disuse and real or simulated microgravity.This study provides evidence that the atrophic processes areevoked rapidly and within 72 h of unloading and suggests thatcountermeasures should be employed in the early stages of spacemissions to offset or prevent muscle loss during the periodwhen the rate of muscle atrophy is the highest.
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