AMPK Mediates Muscle Mass Change But Not the Transition of Myosin Heavy Chain Isoforms during Unloading and Reloading of Skeletal Muscles in Mice

5′AMP-activated protein kinase (AMPK) plays an important role in the regulation of skeletal muscle mass and fiber-type distribution. However, it is unclear whether AMPK is involved in muscle mass change or transition of myosin heavy chain (MyHC) isoforms in response to unloading or increased loading. Here, we checked whether AMPK controls muscle mass change and transition of MyHC isoforms during unloading and reloading using mice expressing a skeletal-muscle-specific dominant-negative AMPKα1 (AMPK-DN). Fourteen days of hindlimb unloading reduced the soleus muscle weight in wild-type and AMPK-DN mice, but reduction in the muscle mass was partly attenuated in AMPK-DN mice. There was no difference in the regrown muscle weight between the mice after 7 days of reloading, and there was concomitantly reduced AMPKα2 activity, however it was higher in AMPK-DN mice after 14 days reloading. No difference was observed between the mice in relation to the levels of slow-type MyHC I, fast-type MyHC IIa/x, and MyHC IIb isoforms following unloading and reloading. The levels of 72-kDa heat-shock protein, which preserves muscle mass, increased in AMPK-DN-mice. Our results indicate that AMPK mediates the progress of atrophy during unloading and regrowth of atrophied muscles following reloading, but it does not influence the transition of MyHC isoforms.

Lactate increases myotube diameter via activation of MEK/ERK pathway in C2C12 cells

AIM

Lactate is produced in and released from skeletal muscle cells. Lactate receptor, G-protein-coupled receptor 81 (GPR81), is expressed in skeletal muscle cells. However, a physiological role of extracellular lactate on skeletal muscle is not fully clarified. The purpose of this study was to investigate extracellular lactate-associated morphological changes and intracellular signals in C2C12 skeletal muscle cells.

METHODS

Mouse myoblast C2C12 cells were differentiated for 5 days to form myotubes. Sodium lactate (lactate) or GPR81 agonist, 3,5-dihydroxybenzoic acid (3,5-DHBA), was administered to the differentiation medium.

RESULTS

Lactate administration increased the diameter of C2C12 myotubes in a dose-dependent manner. Administration of 3,5-DHBA also increased myotube diameter. Not only lactate but also 3,5-DHBA upregulated the phosphorylation level of mitogen-activated protein kinase kinase 1/2 (MEK1/2), p42/44 extracellular signal-regulated kinase-1/2 (ERK1/2) and p90 ribosomal S6 kinase (p90RSK). MEK inhibitor U0126 depressed the phosphorylation of ERK-p90RSK and increase in myotube diameter induced by lactate. On the other hand, both lactate and 3,5-DHBA failed to induce significant responses in the phosphorylation level of Akt, mammalian target of rapamycin, p70 S6 kinase and protein degradation-related signals.

CONCLUSION

These observations suggest that lactate-associated increase in the diameter of C2C12 myotubes is induced via activation of GRP81-mediated MEK/ERK pathway. Extracellular lactate might have a positive effect on skeletal muscle size.

Sagittal alignment and mobility of the thoracolumbar spine are associated with radiographic progression of secondary hip osteoarthritis

OBJECTIVE

To identify predictors of radiographic progression of hip osteoarthritis (OA) over 12 months among functional hip impairments and spinal alignment and mobility.

DESIGN

Fifty female patients with secondary hip OA, excluding those with end-stage hip OA, participated in this prospective cohort study. Joint space width (JSW) of the hip was measured at baseline and 12 months later. With radiographic progression of hip OA over 12 months (>0.5 mm in JSW) as dependent variable, logistic regression analyses were performed to identify predictors for hip OA progression among functional impairments of the hip and spine with and without adjustment for age, body mass index (BMI), and minimum JSW at baseline. The independent variables were hip pain, Harris hip score (HHS), hip morphological parameters, hip passive range of motion (ROM) and muscle strength, and alignment and mobility of the thoracolumbar spine at baseline.

RESULTS

Twenty-one (42.0%) patients demonstrated radiographic progression of hip OA. Multivariable logistic regression analysis showed that larger anterior inclination of the spine in standing position (adjusted OR [95% CI], 1.37 [1.04-1.80]; P = 0.028) and less thoracolumbar spine mobility (adjusted OR [95% CI], 0.96 [0.92-0.99]; P = 0.037) at baseline were statistically significantly associated with radiographic progression of hip OA, even after adjustment for age, BMI, and minimum JSW.

CONCLUSIONS

The findings suggest that spinal alignment and mobility should be considered when assessing risk and designing preventive intervention for radiographic progression of secondary hip OA.

[A case of mitochondrial disease with multiple mitochondrial DNA deletions suspected amyotrophic lateral sclerosis-frontotemporal dementia]

A 76-year-old woman showed a dramatic lowering of her tone of voice in October 2014, followed by muscle weakness of the left arm. The previous attending physician noticed remarkable left dominant frontotemporal lobe atrophy on cranial MRI. Her dysarthria, dysphagia and the muscle weakness of her extremities worsened, and a muscle biopsy revealed mitochondrial abnormality. The mitochondrial DNA from her muscle showed multiple deletions; the previous physician therefore diagnosed the patient with mitochondrial disease. The patient resembled amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD). No other cases of ALS-FTD with mitochondrial disease have been reported in Japan. We therefore consider the present case to be valuable.

Randomized controlled trial of S-1 versus docetaxel in patients with non-small-cell lung cancer previously treated with platinum-based chemotherapy (East Asia S-1 Trial in Lung Cancer)

BACKGROUND

Chemotherapy remains a viable option for the management of advanced non-small-cell lung cancer (NSCLC) despite recent advances in molecular targeted therapy and immunotherapy. We evaluated the efficacy of oral 5-fluorouracil-based S-1 as second- or third-line therapy compared with standard docetaxel therapy in patients with advanced NSCLC.

PATIENTS AND METHODS

Patients with advanced NSCLC previously treated with ≥1 platinum-based therapy were randomized 1 : 1 to docetaxel (60 mg/m2 in Japan, 75 mg/m2 at all other study sites; day 1 in a 3-week cycle) or S-1 (80-120 mg/day, depending on body surface area; days 1-28 in a 6-week cycle). The primary endpoint was overall survival. The non-inferiority margin was a hazard ratio (HR) of 1.2.

RESULTS

A total of 1154 patients (577 in each arm) were enrolled, with balanced patient characteristics between the two arms. Median overall survival was 12.75 and 12.52 months in the S-1 and docetaxel arms, respectively [HR 0.945; 95% confidence interval (CI) 0.833-1.073; P = 0.3818]. The upper limit of 95% CI of HR fell below 1.2, confirming non-inferiority of S-1 to docetaxel. Difference in progression-free survival between treatments was not significant (HR 1.033; 95% CI 0.913-1.168; P = 0.6080). Response rate was 8.3% and 9.9% in the S-1 and docetaxel arms, respectively. Significant improvement was observed in the EORTC QLQ-C30 global health status over time points in the S-1 arm. The most common adverse drug reactions were decreased appetite (50.4%), nausea (36.4%), and diarrhea (35.9%) in the S-1 arm, and neutropenia (54.8%), leukocytopenia (43.9%), and alopecia (46.6%) in the docetaxel arm.

CONCLUSION

S-1 is equally as efficacious as docetaxel and offers a treatment option for patients with previously treated advanced NSCLC.

CLINICAL TRIAL NUMBER

Japan Pharmaceutical Information Center, JapicCTI-101155.

Long Term Changes in Muscles around the Knee Joint after ACL Resection in Rats: Comparisons of ACL-Resected, Contralateral and Normal Limb

The purpose of this study was to investigate the long-term effects of anterior cruciate ligament (ACL) resection on the morphological and contractile characteristics of rectus femoris (RF) and semimembranosus (SM) muscles in both injured and contralateral hindlimbs in rats. Wistar male rats (8-week old) were used. Rats were divided into two groups; ACL-resected and (sham-operated) control groups. Furthermore, right and left limbs of rats in the ACL-resected group were assigned as ACL-resected and contralateral groups, respectively, at 1 day, 1, 4, and 48 weeks after ACL resection. No ACL-resection-associated changes in the mass of both muscles were observed 1 week after ACL resection. On the other hand, ACL-resection-associated reduction on mean fiber cross-sectional area (fiber CSA) in RF muscle lasted 48 weeks after ACL resection. Furthermore, ACL-resection associated increase in fiber composition of type I fiber in RF muscle in contralateral limbs. In addition, long-term effects of ACL resection were observed in both ACL-resected and contralateral limbs. Evidences from this study suggested that ACL resection may cause to change in the morphological (fiber CSA) and contractile (distribution of fiber types) properties of skeletal muscles around the knee joint in not only injured but also contralateral limb. Rehabilitation for quantitative and qualitative muscle changes by ACL resection may be required a special care for a long-term period.