Effects of Maca on Muscle Hypertrophy in C2C12 Skeletal Muscle Cells.

With aging, sarcopenia and the associated locomotor disorders, have become serious problems. The roots of maca contain active ingredients (triterpenes) that have a preventive effect on sarcopenia. However, the effect of maca on muscle hypertrophy has not yet been investigated. The aim of this study was to examine the effects and mechanism of maca on muscle hypertrophy by adding different concentrations of yellow maca (0.1 mg/mL and 0.2 mg/mL) to C2C12 skeletal muscle cell culture. Two days after differentiation, maca was added for two days of incubation. The muscle diameter, area, differentiation index, and multinucleation, were assessed by immunostaining, and the expression levels of the proteins related to muscle protein synthesis/degradation were examined by Western blotting. Compared with the control group, the muscle diameter and area of the myotubes in the maca groups were significantly increased, and the cell differentiation index and multinucleation were significantly higher in the maca groups. Phosphorylation of Akt and mTOR was elevated in the maca groups. Maca also promoted the phosphorylation of AMPK. These results suggest that maca may promote muscle hypertrophy, differentiation, and maturation, potentially via the muscle hypertrophic signaling pathways such as Akt and mTOR, while exploring other pathways are needed.

Moderate hypoxia promotes skeletal muscle cell growth and hypertrophy in C2C12 cells.

Although several studies have implied that a hypoxic environment may be a factor that influences muscle hypertrophy, scant attention has been paid to the effect of oxygen molecules on the morphological characteristics of muscle. The purpose of the present study was to examine the effect of semisevere (i.e., 5%) to moderate (i.e., 10% or 15%) hypoxic environments on the morphological characteristics of skeletal muscle and the associated mechanisms. C2C12 skeletal muscle cells were divided into various groups, namely, the normoxia group (20.9% O2) and hypoxia groups (5% O2, 10% O2, and 15% O2), and cell growth and the expression of associated proteins in the hypoxia groups were compared with those in the normoxia group. The myotube diameter and cell differentiation index were determined on day 6 by immunocytochemical analyses. The expression of proteins associated with muscle cell differentiation (MyoD and myogenin) and muscle hypertrophy (mTOR and p70s6K) were analyzed by Western blotting. We found that compared with normoxia, a 5% oxygen environment inhibited differentiation and caused muscle atrophy. However, compared with normoxia, a 10% oxygen environment promoted muscle differentiation, and 10% oxygen and 15% oxygen environments induced muscle hypertrophy. Compared with normoxia, a 10% oxygen environment promoted myogenin and the expression of mTOR, p70s6K, and the metabolic signal AMPK. We concluded that a hypoxic environment, if not too severe, may promote muscle differentiation and hypertrophy by increasing the expression of proteins associated with muscle cell differentiation and hypertrophy.

Fucoxanthinol attenuates oxidative stress-induced atrophy and loss in myotubes and reduces the triacylglycerol content in mature adipocytes.

The combination of sarcopenia and obesity (i.e., sarcopenic obesity) is more strongly associated with disability and metabolic/cardiovascular diseases than obesity or sarcopenia alone. Therefore, countermeasures that simultaneously suppress fat gain and muscle atrophy to prevent an increase in sarcopenic obesity are warranted. The aim of this study was to investigate the simultaneous effects of fucoxanthinol (FXOH) on fat loss in mature adipocytes and the inhibition of atrophy and loss in myotubes induced by oxidative stress. C2C12 myotubes were treated with FXOH for 24 h and further incubated with hydrogen peroxide (H2O2) for 24 h. The area of myosin heavy chain-positive myotubes and the ROS concentration were measured. Mature 3T3-L1 adipocytes were treated with FXOH for 72 h. The triacylglycerol (TG) content and glycerol and fatty acid (FA) release were biochemically measured. The myotube area was smaller in H2O2-treated cells than that in control cells. However, FXOH protected against the H2O2-induced decreases in myotube area. Further, the ROS concentration was significantly higher in the FXOH-treated cells compared with that in the control cells, although it was significantly lower than that in the H2O2-treated cells. On the other hand, in the mature adipocytes, the TG content was significantly decreased by FXOH treatment compared to that in the control. Moreover, FXOH treatment significantly increased glycerol and FA release compared with that of the control. These results suggest that FXOH inhibits H2O2-induced atrophy and loss in myotubes and activates lipolysis and decreases the TG content in mature adipocytes. Accordingly, FXOH has the potential to exert anti-sarcopenic obesity effects.

Mechanical unloading of 3D-engineered muscle leads to muscle atrophy by suppressing protein synthesis.

Three-dimensional (3D)-engineered muscle is an useful approach to a more comprehensive understanding of molecular mechanisms underlying unloading-induced muscle atrophy. We investigated the effects of mechanical unloading on molecular muscle protein synthesis (MPS)- and muscle protein breakdown (MPB)-related signaling pathways involved in muscle atrophy in 3D-engineered muscle, and to better understand in vitro model of muscle disuse. The 3D-engineered muscle consisting of C2C12 myoblasts and type-1 collagen gel was allowed to differentiate for 2 wk and divided into three groups: 0 days of stretched-on control (CON), 2 and/or 7 days of stretched-on (ON), in which both ends of the muscle were fixed with artificial tendons, and the stretched-off group (OFF), in which one side of the artificial tendon was detached. Muscle weight (-38.1% to -48.4%), length (-67.0% to -73.5%), twitch contractile force (-70.5% to -75.0%), and myosin heavy chain expression (-32.5% to -50.5%) in the OFF group were significantly decreased on days 2 and 7 compared with the ON group (P < 0.05, respectively), despite that ON group was stable over time. Although determinative molecular signaling could not be identified, the MPS rate reflected by puromysin-labeled protein was significantly decreased following mechanical unloading (P < 0.05, -38.5% to -51.1%). Meanwhile, MPB, particularly the ubiquitin-proteasome pathway, was not impacted. Hence, mechanical unloading of 3D-engineered muscle in vitro leads to muscle atrophy by suppressing MPS, cell differentiation, and cell growth rather than the promotion of MPB.NEW & NOTEWORTHY Three-dimensional (3D)-engineered muscles have recently been shown to closely replicate the in vivo architecture. We found that mechanical unloading of 3D-engineered muscle led to muscle disuse atrophy accompanied by reduced functional properties and contractile protein expression via suppression of muscle protein synthesis. This novel model may improve the in vitro testing of modalities with the potential to reduce mechanical unloading-induced atrophy.

Effects of Fucoxanthin on the Inhibition of Dexamethasone-Induced Skeletal Muscle Loss in Mice.

Fucoxanthin (Fx) has preventive effect against muscle atrophy and myotube loss in vitro, but it has not yet been examined in vivo. Therefore, we aimed to investigate the effect of Fx on dexamethasone (Dex)-induced muscle atrophy and fat mass in mice. ICR mice were fed with Fx diets from 2 weeks before Dex treatment to the end of the study. Muscle atrophy was induced in the mice by oral administration of Dex. Body weight was significantly lower by Dex treatment. Visceral fat mass in the Fx-treated group were significantly lower than those in the control group. The Dex-induced decrease in tibialis anterior muscle mass was ameliorated by Fx treatment. Fx treatment significantly attenuated muscle lipid peroxidation compared with the control and Dex-treated groups. The phosphorylation of AMPK was significantly higher in the Dex-treated group than in the control group. The expression of cytochrome c oxidase (COX) IV was significantly higher in the Fx-treated group than in the control group. These results suggest that Fx may be a beneficial material to prevent muscle atrophy in vivo, in addition to the effect of fat loss.

Infectious prion protein in the filtrate even after 15 nm filtration.

The evaluation of the removal efficacy during manufacturing is important for the risk assessment of plasma products with respect to possible contamination by infectious prions, as recently reported in several papers on the potential for prion transmission through plasma products. Here, we evaluated a virus removal filter which has 15 nm pores. An antithrombin sample immediately prior to nano-filtration was spiked with prion material prepared in two different ways. The removal (log reduction factor) of prion infectivity using animal bioassays was >or=4.72 and 4.00 in two independent filtrations. However, infectivity was detected in both the pellet and supernatant following ultracentrifugation of the 15 nm filtered samples, indicating difficulty in complete removal. The data supports the conclusion that a certain amount of infectious prion protein is present as a smaller and/or soluble form (less than approximately 15 nm in diameter).

Conduction Velocity of Muscle Action Potential of Knee Extensor Muscle During Evoked and Voluntary Contractions After Exhaustive Leg Pedaling Exercise.

PURPOSE: Muscle fiber conduction velocity (CV) has been developed to estimate neuromuscular fatigue and measured during voluntary (VC) and electrically evoked (EC) contractions. Since CV during VC and EC reflect different physiological phenomena, the two parameters would show inconsistent changes under the conditions of neuromuscular fatigue. We investigated the time-course changes of CV during EC and VC after fatiguing exercise. METHODS: In 14 young males, maximal voluntary contraction (MVC) of knee extensor muscles, CV during electrical stimulation (CV-EC) and MVC (CV-VC) were measured before and immediately, 30 min, 60 min, 120 min, and 24 h after exhaustive leg pedaling exercise. RESULTS: CV-EC significantly increased immediately after the fatiguing exercise (p < 0.05) and had a significant negative correlation with MVC in merged data from all time-periods (r = -0.511, p < 0.001). CV-VC significantly decreased 30, 60, and 120 min after the fatiguing exercise (p < 0.05) and did not show any correlations with MVC (p > 0.05). CONCLUSION: These results suggest that CV during EC and VC exhibits different time-course changes, and that CV during EC may be appropriate to estimate the degree of neuromuscular fatigue after fatiguing pedaling exercise.

Specific characterization of regional storage fat in upper and lower limbs of young healthy adults.

This study aimed to determine the specific characterization of regional storage fat in the upper limb as compared to the lower limb of young healthy adults. The regional storage fat and skeletal muscle in upper and lower limbs were obtained by magnetic resonance imaging (MRI) and multifrequency bioelectrical impedance analysis (BIA). For MRI measurements, images at the continuous anatomical cross-sectional areas of subcutaneous adipose tissue and skeletal muscle in the upper arm and thigh were selected for the analysis. Values measured by MRI were larger than those measured by BIA. MRI data showed that the percentage of fat was significantly higher in the upper arm compared to the thigh in both men and women. This study suggests that BIA results in a significantly different estimation of the whole body and limb composition when compared to MRI and that MRI is useful to determine regional specificities in the limb composition. From these quantified evaluation, we found significantly large amount of regional storage fat in upper limbs of young healthy adults, especially women.