Mild Hyperbaric Oxygen Inhibits Growth-related Decrease in Muscle Oxidative Capacity of Rats with Metabolic Syndrome

Aim: We examined the effects of mild hyperbaric oxygen on the properties of the soleus muscle in rats with metabolic syndrome. Methods: Five-week-old metabolic syndrome (SHR/NDmcr-cp, cp/cp) rats were divided into normobaric (CP) and mild hyperbaric oxygen (CP-H) groups (n = 5/group). In addition, 5-week-old Wistar rats were assigned as the normobaric control (WR) group (n = 5). The CP-H group was exposed to 1.25 atmospheres absolute with 36% oxygen for 3 h daily for 16 weeks. Succinate dehydrogenase (SDH) activity and mRNA levels of peroxisome proliferator-activated receptor γ coactivator-1α (Pgc-1α) in the soleus muscle were examined. The fiber type composition, cross-sectional areas, and SDH staining intensity in the soleus muscle were also examined. Results: The CP-H group showed lower fasting and nonfasting blood glucose, glycated hemoglobin, total cholesterol, triglyceride, insulin, and systolic blood pressure levels; higher adiponectin levels; and higher SDH activity and mRNA levels of Pgc-1α in the muscle than the CP group. Compared with the CP group, the CP-H group had a lower percentage of type I fibers and observed type IIA fibers in the muscle. The CP-H group also had higher SDH staining intensity of type I and type IIC fibers in the muscle than the CP group. No differences in these values were observed in the muscles of the WR and CP-H groups. Conclusion: Mild hyperbaric oxygen inhibited growth-related increase in blood glucose levels and decrease in muscle oxidative capacity of rats with metabolic syndrome because of improved oxidative metabolism.