It is known that repeated bouts of high-intensity interval training (HIIT) lead to enhanced levels of glycolysis, glycogenesis, and lactate transport proteins in skeletal muscle; however, little is known about the molecular mechanisms underlying these adaptations. To decipher the mechanism leading to improvement of skeletal muscle glycolytic capacity associated with HIIT, we examined the role of hypoxia-inducible factor-1α (Hif-1α), the major transcription factor regulating the expression of genes related to anaerobic metabolism, in the adaptation to HIIT. First, we induced Hif-1α accumulation using ethyl 3,4-dihydroxybenzoate (EDHB) to assess the potential role of Hif-1α in skeletal muscle. Treatment with EDHB significantly increased the protein levels of Hif-1α in gastrocnemius muscles, accompanied by elevated expression of genes related to glycolysis, glycogenesis, and lactate transport. Daily administration of EDHB for 1 wk resulted in elevated glycolytic enzyme activity in gastrocnemius muscles. Second, we examined whether a single bout of HIIT could induce Hif-1α protein accumulation and subsequent increase in the expression of genes related to anaerobic metabolism in skeletal muscle. We observed that the protein levels of Hif-1α and expression of the target genes were elevated 3 h after an acute bout of HIIT in gastrocnemius muscles. Last, we examined the effects of long-term HIIT. We found that long-term HIIT increased the basal levels of Hif-1α as well as the glycolytic capacity in gastrocnemius muscles. Our results suggest that Hif-1α is a key regulator in the metabolic adaptation to high-intensity training.

Adipose tissue has been classified into white adipose tissue (WAT), brown adipose tissue (BAT), and beige adipose tissue the latter of which is produced as WAT changes into BAT due to exposure to cold temperature or exercise. In response to these stimulations, WAT produces heat by increasing mitochondrial contents and the expression of uncoupling protein 1 (UCP1), thus facilitating browning. Exercise is known to be one of the triggers for WAT browning, but the effects of exercise intensity on the browning of WAT remain to be unclear. Therefore, in this study, we aimed to examine the effects of high‐ or low‐intensity exercises on the browning of WAT. Mice performed high‐ or low‐intensity running on a treadmill running 3 days a week for four weeks. As per our findings, it was determined that four weeks of running did not significantly reduce inguinal WAT (iWAT) wet weight but did significantly reduce adipocytes size, regardless of exercise intensity. The protein expression level of UCP1 was significantly increased in iWAT by high‐intensity running. In addition, the expression of oxidative phosphorylation proteins (OXPHOS) in iWAT was significantly increased by high‐intensity running. These results demonstrated that high‐intensity exercise might be effective for increasing mitochondrial contents and heat production capacity in iWAT. Furthermore, we found that high‐intensity running increased the protein expression level of fibroblast growth factor 21 (FGF21) in skeletal muscle compared with that in low intensity running. We have also examined the relationship between browning of WAT and the expression of FGF21 in skeletal muscle and found a positive correlation between the protein expression of UCP1 in iWAT and the protein expression of FGF21 in gastrocnemius muscle. In conclusion, we suggest that high‐intensity exercise is effective for the browning of WAT and the increase of FGF21 in skeletal muscle.

Despite the World Anti-Doping Agency (WADA) ban on gene doping in the context of advancements in gene therapy, the risk of EPO gene-based doping among athletes is still present. To address this and similar risks, gene-doping tests are being developed in doping control laboratories worldwide. In this regard, the present study was performed with two objectives: to develop a robust gene-doping mouse model with the human EPO gene (hEPO) transferred using recombinant adenovirus (rAdV) as a vector and to develop a detection method to identify gene doping by using this model. The rAdV including the hEPO gene was injected intravenously to transfer the gene to the liver. After injection, the mice showed significantly increased whole-blood red blood cell counts and increased expression of hematopoietic marker genes in the spleen, indicating successful development of the gene-doping model. Next, direct and potentially indirect proof of gene doping were evaluated in whole-blood DNA and RNA by using a quantitative PCR assay and RNA sequencing. Proof of doping could be detected in DNA and RNA samples from one drop of whole blood for approximately a month; furthermore, the overall RNA expression profiles showed significant changes, allowing advanced detection of hEPO gene doping.

The purposes of our study were to examine (1) Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg) expressions in mouse skeletal muscle; and (2) the effect of 6‐week training on Rhbg and Rhcg expressions. The levels of Rhbg and Rhcg expressions were much higher in the soleus (Sol) than in the plantaris (Pla) or gastrocnemius (Gas). Immunofluorescence microscopy demonstrated that Rhbg colocalizes with dystrophin, a plasma membrane protein marker, whereas Rhcg colocalizes with CD31, a vascular endothelial cell marker. In a 6‐week swim training study, we set up two different training groups. Endurance (END) group underwent swim training without load for 30 min and exercise time was increased by 30 min every 2 weeks. High‐intensity interval training (HIIT) group underwent 10–12 sets of swim training at 20 sec per set and intervals of 10 sec, with a load of 10% body weight. After 6 weeks of training, all mice performed exhaustive swimming performance test (PT), with 9% of body weight to exhaustion. HIIT group could significantly swim more and showed significantly lower blood ammonia level compared with control (CON) group at immediately after PT. Rhbg and Rhcg levels did not change after 6 weeks in both END and HIIT groups. Our results indicate that ammonia transporters are more abundant in slow fiber than fast fiber muscles and 6 weeks swim training suppresses blood ammonia elevation induced by high‐intensity exercise with performance improvement, although the levels of ammonia transporter proteins does not change.