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Kanazashi M1, Tanaka M2, Maeshige N3, Fijino H3
1Prefectural University of Hiroshima, Mihara, Japan, 2Osaka University of Human Sciences, Settsu, Japan, 3Kobe University, Kobe, Japan
Background: Chronic neuromuscular inactivity induces quantitative and qualitative changes in skeletal muscle such as muscle atrophy and impaired oxidative metabolism. We have reported that resistance training using electrical stimulation (ES) attenuates muscle atrophy in hindlimb unloaded rat, an in vivo model of disuse. However, ES has little effect on a disused-related decline in muscle oxidative capacity caused by mitochondrial loss and capillary regression. In contrast, antioxidant treatment with astaxanthin attenuates a loss of mitochondria and capillaries in disused muscle. Therefore, we hypothesized that a combinational treatment with ES and astaxanthin supplementation during unloading would attenuate both the muscle atrophy and the impaired oxidative capacity in unloaded muscle.
Purpose: The purpose of the present study is to investigate the combinational effects of ES and antioxidant treatment on muscle mass and oxidative capacity in unloaded rats.
Methods: Male Sprague Dawley rats were used. The animals were randomly divided into 5 groups as follow: control, hindlimb unloading (HU), hindlimb unloading with astaxanthin (HU+AX), hindlimb unloading with electrical stimulation (HU+ES) and hindlimb unloading with a combination of astaxanthin supplementation and electrical stimulation (HU+AX+ES) groups. The animals in the HU+AX and HU+AX+ES groups were orally administrated with astaxanthin oil by a feeding needle twice a day (total of 100 mg/kg/day) during a week of unloading. The animals in the HU+ES and HU+AX+ES groups were subjected to electrical stimulation of the calf muscles twice a day during the unloading period. The total stimulation duration was 240 s per day. At the end of the experiment, soleus muscle was excised and used for subsequent histochemical and molecular biological measurements. Significant differences between groups were determined using one-way ANOVA followed by Tukey's post hoc test to determine specific group differences. Results were deemed statistically significant level at p 0.05.
Results: HU led to a decreased muscle mass and fiber cross-sectional areas, a reduction of phosphorylated FoxO3 protein expression and an increase in ubiquitinated protein expression. Furthermore, HU resulted in not only a decrease in capillary number, integrated SDH activity, a maker for mitochondrial volume, and protein expression of PGC-1α, a key factor for mitochondrial biogenesis and angiogenesis, but also an increase in Reactive Oxygen Species production, an indicator for oxidative stress, within the muscle. ES alone attenuated the muscle atrophy but had no impact on oxidative stress and mitochondrial loss due to HU. On the other hand, ES combined with astaxanthin supplementation attenuated the muscle atrophy and maintained the capillary number and integrated SDH activity near control values. Additionally, the combination suppressed the decline in FoxO3 phosphorylation, increase in protein ubiquitination and downregulation of PGC-1α within the unloaded muscle.
Conclusion(s): The present study indicates that the combinational intervention with ES and antioxidant astaxanthin supplementation during unloading is effective for both the muscle atrophy and the impaired oxidative capacity through different mechanisms.
Implications: These results suggest that this combined treatment approach may be effective as a therapeutic strategy in other conditions involving muscular loss and dysfunction. This implicates the importance of performing physical therapy under an appropriate nutritional management.
Keywords: Skeletal muscle, Muscle atrophy, Oxidative stress
Funding acknowledgements: This work was supported by JSPS KAKENHI Grant Numbers 15K16516 and 17K18028.
Purpose: The purpose of the present study is to investigate the combinational effects of ES and antioxidant treatment on muscle mass and oxidative capacity in unloaded rats.
Methods: Male Sprague Dawley rats were used. The animals were randomly divided into 5 groups as follow: control, hindlimb unloading (HU), hindlimb unloading with astaxanthin (HU+AX), hindlimb unloading with electrical stimulation (HU+ES) and hindlimb unloading with a combination of astaxanthin supplementation and electrical stimulation (HU+AX+ES) groups. The animals in the HU+AX and HU+AX+ES groups were orally administrated with astaxanthin oil by a feeding needle twice a day (total of 100 mg/kg/day) during a week of unloading. The animals in the HU+ES and HU+AX+ES groups were subjected to electrical stimulation of the calf muscles twice a day during the unloading period. The total stimulation duration was 240 s per day. At the end of the experiment, soleus muscle was excised and used for subsequent histochemical and molecular biological measurements. Significant differences between groups were determined using one-way ANOVA followed by Tukey's post hoc test to determine specific group differences. Results were deemed statistically significant level at p 0.05.
Results: HU led to a decreased muscle mass and fiber cross-sectional areas, a reduction of phosphorylated FoxO3 protein expression and an increase in ubiquitinated protein expression. Furthermore, HU resulted in not only a decrease in capillary number, integrated SDH activity, a maker for mitochondrial volume, and protein expression of PGC-1α, a key factor for mitochondrial biogenesis and angiogenesis, but also an increase in Reactive Oxygen Species production, an indicator for oxidative stress, within the muscle. ES alone attenuated the muscle atrophy but had no impact on oxidative stress and mitochondrial loss due to HU. On the other hand, ES combined with astaxanthin supplementation attenuated the muscle atrophy and maintained the capillary number and integrated SDH activity near control values. Additionally, the combination suppressed the decline in FoxO3 phosphorylation, increase in protein ubiquitination and downregulation of PGC-1α within the unloaded muscle.
Conclusion(s): The present study indicates that the combinational intervention with ES and antioxidant astaxanthin supplementation during unloading is effective for both the muscle atrophy and the impaired oxidative capacity through different mechanisms.
Implications: These results suggest that this combined treatment approach may be effective as a therapeutic strategy in other conditions involving muscular loss and dysfunction. This implicates the importance of performing physical therapy under an appropriate nutritional management.
Keywords: Skeletal muscle, Muscle atrophy, Oxidative stress
Funding acknowledgements: This work was supported by JSPS KAKENHI Grant Numbers 15K16516 and 17K18028.
Topic: Musculoskeletal: lower limb; Musculoskeletal: lower limb
Ethics approval required: Yes
Institution: Kobe University
Ethics committee: Kobe University of ethics committee
Ethics number: P130903
All authors, affiliations and abstracts have been published as submitted.
