Recently, fasting has been spotlighted from a healthcare perspective. However, the de-tailed biological mechanisms and significance by which the effects of fasting confer health benefits are not yet clear. Due to certain advantages of zebrafish, as a vertebrate model widely utilized in biological studies, we used mRNA-sequencing and bioinformatics analysis to examine comprehensive gene expression changes in skeletal muscle tissues during fasting-refeeding. Our results produced a novel set of nutrition-related genes under a fasting-refeeding protocol. We found five dramatically upregulated genes in each fasting (for 24 hours) and refeeding (after 3 hours), exhibiting a rapid response to the provided conditional changes. The assessment of the gene length revealed, the gene set whose expression was elevated only after 3 hours of refeeding had a shorter length, suggesting that nutrition-related gene function is associated with gene length. Taken together, our results from bioinformatics analyses provide new insights into biological mechanisms induced by fasting-refeeding conditions within zebrafish skeletal muscle.

Plasma cell-free DNA (cfDNA) is frequently analyzed using liquid biopsy to investigate cancer markers. Accordingly, we hypothesized this concept could be applied to the field of exercise physiology. Here, we aimed to identify specific cfDNA (spcfDNA) sequences in the plasma of non-treated human participants using next generation sequencing (NGS) and to clearly define the dynamics regarding the amounts of spcfDNA-fragments upon extreme exercise, such as running a full marathon. NGS analysis was performed using cfDNA of pooled plasma collected from non-treated participants. We confirmed the TaqMan-qPCR assay had a high sensitivity and found the spcfDNA sequence abundance was 16,600-fold higher than a normal genomic region. We then used the TaqMan-qPCR assay to investigate the dynamics of the levels of spcfDNA-fragments upon running a full marathon. Quantities of the spcfDNA fragments were significantly increased post marathon. Furthermore, the amounts of spcfDNA fragments strongly correlated with the numbers of white blood cells and plasma myoglobin concentrations. These results suggest the spcfDNA fragments identified in this study were highly sensitive response markers to extreme physical stress. The findings of this study may provide new insights into exercise physiology and genome biology on the human.

Loss of muscle mass and strength are progressing with aging. Exercise is a beneficial method to prevent physical disfunction and habitual exercise improve the muscle quality. Therefore, we evaluated the effects of a long-term habitual exercise on the senescence-accelerated mice prone8 (SAMP8). 27wk SAMP8 were used in this study. Mice were classified into 28 (28w) and 44 weeks old. The 44-week group was divided into the sedentary group (44w) and a group exercising for 16 weeks (44w+Ex). The 44w+Ex performed habitual exercise from 28 to 44 weeks. Additionally, grip strength tests were performed with mice aged 28 and 44 weeks. Mice were dissected and collected muscle samples and measured muscle weight at 44w. Gastrocnemius was decreased in 44w but were unchanged in 44w+Ex. Grip strength in 44w was lower trend, but there was no change in 44w+Ex. The phosphorylation levels of Akt and p70S6K as a protein synthesis marker were decreased in 44w. Cytochrome c oxidase subunit IV(COXIV) mRNA and protein levels decreased in 44w. These results suggested that long-term habitual exercise attenuated muscle mass and strength decline through improving muscle protein synthesis and mitochondrial function. In conclusion, long-term habitual exercise attenuated muscle mass and strength decline.

Muscle mass and strength decrease with aging, but habitual exercise can maintain muscle health. β-Hydroxy-β-methyl butyrate calcium (HMB) and black ginger (BG) are anti-oxidants that have been reported to improve muscle protein metabolism and energy production; these molecules may have synergistic effects. The senescence-accelerated mouse-prone 8 (SAMP8) model is a useful model of muscle aging. Therefore, in this study, we explored how the combination of habitual exercise, HMB, and BG affected muscle aging. We used 28-week-old SAMP8 mice divided into five groups: control, exercise (Ex), Ex+BG, Ex+HMB, and Ex+BG+HMB (Ex+Comb). Mice were required to run on a treadmill for 16 weeks at 5 days per week. In 44-week-old mice, grip strength tests and dissection were conducted. Muscle weight was measured, and the gastrocnemius muscle was subjected to quantitative polymerase chain reaction and immunoblotting. Muscle mass and strength were preserved in the Ex+Comb group, and mitochondrial function was preserved through suppressing oxidative stress. Muscle protein synthesis signaling was improved in the Ex+Comb group. Autophagy and the ubiquitin system were normalized by Ex+Comb treatment. Overall, habitual exercise and HMB plus BG treatment maintained muscle health by suppressing oxidative stress, preserving mitochondrial function, and maintaining muscle protein metabolism in SAMP8 mice.

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been rapidly increasing worldwide. A choline-deficient L-amino acid-defined high fat diet (CDHFD) has been used to create a mouse model of nonalcoholic steatohepatitis (NASH). There are some reports about the effects on mice of being fed CDAHFD for a long time, 1 to 3 months. However, the effect of this diet over a short period has been unknown. Therefore, we examined the effect of one week of feeding CDAHFD on the mouse liver. Feeding this diet for only one week induced lipid droplet deposition in the liver with increasing activity of liver-derived enzymes in the plasma. On the other hand, it did not induce fibrosis and cirrhosis. Additionally, it was demonstrated that mitochondrial respiration is significantly impaired with severe oxidative stress in the liver by CDAHFD, associated with a decreasing mitochondrial DNA copy number and complexes-proteins. In the gene expression analysis of the liver, inflammatory and oxidative stress markers were significantly increased by CDAHFD. These results demonstrated that one week of feeding CDAHFD to mice induces steatohepatitis with mitochondrial dysfunction and severe oxidative stress, without fibrosis, which can partially mimic the early stage of the NASH in humans.

Exercise affects various organs. However, its effects on nutrient digestion and absorption in the intestinal tract are not well understood. A few studies have reported that exercise training in-creases the expression of carbohydrate digestion and absorption molecules. Exercise was also shown to increase the concentration of blood glucagon like peptide-2(GLP-2), which regulates carbohydrate digestion and absorption in small intestinal epithelium. Therefore, we investigated the effects of exercise on intestinal digestion and absorption molecules and the levels of GLP-2. 6-wk-old of male mice were divided into 2 groups; sedentary (SED) and low-intensity exercise (LEx). LEx mice were required to run on a treadmill (12.5 m/min, 60 min), whereas SED mice rested. All mice were euthanized 1 h after exercise or rest and plasma, jejunum, ileum, and colon were sampled. Samples were analyzed using EIA and immunoblotting. The levels of plasma GLP-2 and the expression of the GLP-2 receptor, sucrase-isomaltase (SI), and glucose transporter (GLUT2) in the jejunum were increased in LEx group. We showed that acute low-intensity exer-cise affects the intestinal carbohydrate digestion and absorption molecules via GLP-2. Our results suggest that exercise might provide new benefits to the small intestine for people with intestinal frailty.

The aim of this study was to clarify degradation characteristics in each tissue of the knee complex of a medial meniscectomy (MMx)-induced knee osteoarthritis (KOA) animal model using classical methods and a new comprehensive evaluation method called contrast-enhanced X-ray micro-computed tomography (CEX-μCT), which was developed in the study. Surgical MMx was performed in the right knee joints of five male Wistar rats to induce KOA. At 4 wk post-surgery, the synovitis was evaluated using qPCR. Degradations of the articular cartilage of the tibial plateau were evaluated using classical methods and CEX-μCT. Evaluation of the synovitis demonstrated significantly increased expression levels of inflammation-associated marker genes in MMx-treated knees compared to that in sham-treated knees. Evaluation of the articular cartilage using classical methods showed that MMx fully induced degradation of the cartilage. Evaluation using CEX-μCT showed that local areas of the medial cartilage of the tibial plateau were significantly reduced in MMx-treated knees compared to that in sham-treated knees. On the other hand, total cartilage volumes were significantly increased in MMx-treated knees. Based on the findings of this study, the researchers in KOA research could be helped to select an optimal KOA model to discover new drugs.

Local cryotherapy is widely used as a treatment for sports-related skeletal muscle injury. However, its molecular mechanisms are unknown. To clarify these mechanisms, in this study, we applied one to three 15-min cold stimulations at 4 °C to various cell lines (in vitro), the tibialis anterior (TA) muscle (ex vivo), and mouse limbs (in vivo). In the in vitro assay, cAMP response element-binding protein 1 (CREB1) was markedly phosphorylated (as pCREB1) and CREB-binding protein (CBP) was recruited to pCREB-1 in response to two or three cold stimulations. In a reporter assay with the cAMP-responsive element, the signals significantly increased after two to three cold stimulations at 4 °C. In the ex vivo study, CREB-targeting genes were significantly upregulated following two or three cold stimulations. The in vivo experiment disclosed that cold stimulation of a mouse limb for 9 days significantly increased mitochondrial DNA copy number and upregulated genes such as Pgc-1α involved in mitochondrial biogenesis. The foregoing results suggest that local cryotherapy increases CREB transcription and upregulates CREB-targeting genes in a manner dependent on cold stimulation frequency and duration. This information may serve as an impetus for further investigations into local cryotherapy as a treatment for sports-related skeletal muscle trauma.

With the rapid progress of genetic engineering and gene therapy, World Anti-Doping Agency has alerted to gene doping and prohibited its use in sports. However, there is no standard method available yet for detection of transgenes delivered by recombinant adenoviral (rAdV) vectors. Here we aimed to develop a detection method for transgenes delivered by rAdV vectors in a mouse model that mimics gene doping. rAdV vectors containing mCherry gene was delivered in mice through intravenous injection or local muscular injection. After five days, stool and whole blood samples were collected, and total DNA was extracted. As additional experiments, whole blood was also collected from mouse tail tip until 15 days from injection of the rAdv vector. Transgene fragments from different DNA samples were analyzed using semi-quantitative PCR (sqPCR), quantitative PCR (qPCR), and droplet digital PCR (ddPCR). In the results, transgene fragments could directly be detected from blood cell fraction-DNA, plasma-cell free DNA and stool-DNA by qPCR and ddPCR, depending on specimen type and injection methods. We observed that a combination of blood cell fraction-DNA and ddPCR was more sensitive than other combinations used in this model. These results could accelerate the development of detection methods for gene doping.

The World Anti-Doping Agency (WADA) has prohibited gene doping in the context of progress in gene therapy. In addition, there is a risk of the EPO gene being applied in gene doping among athletes. Along with this, development of a gene-doping test has been underway in worldwide. Here, we had two purposes: to develop a robust gene doping mouse model using the human EPO gene (hEPO) transferred using recombinant adenovirus (rAdV) as a vector and to develop a detection method to prove gene doping using this model. The rAdV including the hEPO gene were injected intravenously to transfer the gene to the liver. After injection, the mice developed significantly increased red blood cell counts in whole blood and increased gene expressions of hematopoietic markers in the spleen, indicating successful development of the gene doping model. Next, we detected direct and indirect proof of gene doping in whole blood DNA and RNA using qPCR assay and RNA sequencing. Proof was detected in one drop of whole blood DNA and RNA over a long period; furthermore, the overall RNA expression profiles significantly changed. Therefore, we have advanced detection of hEPO gene doping in humans.