Muscle fiber type-dependence effect of exercise on genomic networks in aged mice models.

Skeletal muscles are made up of various muscle fiber type including slow and fast-twitch fibers. Because each muscle fiber has its own physiological characteristics, the effects of aging and exercise vary depending on the type of muscle fiber. We used bioinformatics screening techniques such as differentially expressed gene analysis, gene ontology analysis and gene set enrichment analysis, to try to understand the genetic differences between muscle fiber types. The experiment and gene expression profiling in this study used the soleus (SOL, slow-twitch muscle) and gastrocnemius (GAS, fast-twitch muscle). According to our findings, fatty acid metabolism is significantly up-regulated in SOL compared to GAS, whereas the glucose metabolism pathway is significantly down-regulated in SOL compared to GAS. Furthermore, apoptosis and myogenesis patterns differ between SOL and GAS. SOL did not show differences in apoptosis due to the aging effect, but apoptosis in GAS was significantly up-regulated with age. Apoptosis in GAS of old groups is significantly reduced after 4 weeks of aerobic exercise, but no such finding was found in SOL. In terms of myogenesis, exercise intervention up-regulated this process in GAS of old groups but not in SOL. Taken together, muscle fiber type significantly interacts with aging and exercise. Despite the importance of the interaction between these factors, large-scale gene expression data has rarely been studied. We hope to contribute to a better understanding of the relationship between muscle fiber type, aging and exercise at the molecular level.

Potential role of exercise-induced glucose-6-phosphate isomerase in skeletal muscle function.

PURPOSE: Recent studies have shown that glucose-6-phosphate isomerase (GPI)-which is a glycolysis interconversion enzyme-reduces oxidative stress. However, these studies are limited to tumors such as fibrosarcoma, and there are no studies that have examined the effects of exercise on GPI expression in mice skeletal muscle. Furthermore, GPI acts in an autocrine manner thorough its receptor, autocrine motility factor receptor (AMFR); therefore, we investigated expression level changes of secreted GPI from skeletal muscle in in vitro study to examine the potential role of GPI on skeletal muscle. METHODS: First, we performed an in vitro study, to identify the condition that upregulates GPI levels in skeletal muscle cells; we treated C2C12 muscle cells with an exercise-mimicking chemical, AICAR. AICAR treatment upregulated GPI expression level in C2C12 cell and its secretomes. To confirm the direct effect of GPI on skeletal muscle cells, we treated C2C12 cells with GPI recombinant protein. RESULTS: We found that GPI improved the viability of C2C12 cells. In the in vivo study, the exercise-treated mice group showed upregulated GPI expression in skeletal muscle. Based on the in vitro study results, we speculated that expression level of GPI in skeletal muscle might be associated with muscle function. We analyzed the association between GPI expression level and the grip strength of the all mice group. The mice group's grip strengths were upregulated after 2 weeks of treadmill exercise, and GPI expression level positively correlated with the grip strength. CONCLUSION: These results suggested that the exercise-induced GPI expression in skeletal muscle might have a positive effect on skeletal muscle function.

Predictive factors for invasive intraductal papillary mucinous neoplasm of the pancreas.

BACKGROUNDS/AIMS: Intraductal papillary mucinous neoplasm (IPMN) of the pancreas has malignant potential. Predicting invasive IPMN has proven difficult and controversial. We tried to identify predictive factors for invasive IPMN. METHODS: Thirty six patients underwent resection for IPMN from February 2001 to July 2011. Clinicopathological features including demographic, imaging, microscopic, and serological findings were retrospectively reviewed. Receiver operating characteristic (ROC) curve analysis was used to analyze sensitivity and specificity of all possible cut-off values for the diameter of the main pancreatic duct and mass size predicting invasive IPMN. Student t-test, chi-square test, and logistic regression were used for univariate and multivariate analysis. RESULTS: The mean age was 63.5±8.4 years. Males were more commonly affected (58.3% vs 41.7%). Pancreaticoduodenectomy was performed in 55.6% of patients, distal pancreatectomy in 36.1%, and central pancreatic resection in 8.3%. Non-invasive IPMNs were present in 80.6% (n=29), whereas invasive IPMNs were present in 19.4% (n=7). In univariate analysis, tumor location (p=0.036), Kuroda classification (p=0.048), mural nodule (p=0.016), and main duct dilatation (≥8 mm) (p=0.006) were statistically significant variables. ROC curve analysis showed that a value of 8 mm for the main duct dilatation and a value of 35 mm for the size of the mass lesion have 80% sensitivity and 75% specificity and 100% sensitivity and 82.6% specificity, respectively. However, in multivariate analysis, main ductal dilatation (≥8 mm) was identified to be the only independent factor for invasive IPMN (p=0.049). CONCLUSIONS: Main duct dilatation appears to be a useful indicator for predicting invasive IPMN.