Metabolic syndrome is linked to physical inactivity and consumption of a high-fat and high-calorie diet and is characterized by obesity, high blood pressure, increased blood glucose levels, and hyperlipidemia1). Skeletal muscle is the primary site of insulin action and glucose metabolism. Reduced oxidative capacity in skeletal muscle impairs glucose metabolism and increases the risk of development and aggravation of metabolic syndrome. Metabolic syndrome ultimately develops into lifestyle-related diseases, such as cardiovascular disease, type 2 diabetes, hypertension, and associated complications. Compared with healthy individuals, obese patients with or without type 2 diabetes have a low percentage of high-oxidative type Ⅰ fibers and a high percentage of low-oxidative type Ⅱ fibers, particularly type ⅡB fibers, in the vastus lateralis and rectus abdominis muscles. Previous studies using animal models observed that rats with metabolic syndrome exhibited a low oxidative capacity of the soleus muscle with a decreased percentage of type Ⅰ fibers and an increased percentage of type ⅡA fibers compared with normal rats. One of these studies 12) showed decreased oxidative enzyme activity in type ⅡA fibers of rats with metabolic syndrome compared with normal rats. These results indicate a low oxidative capacity of skeletal muscle in humans and animal models with metabolic syndrome.
Humans and animal models with metabolic syndrome have a low oxidative capacity in skeletal muscle. Reduced oxidative capacity in skeletal muscle impairs glucose metabolism and increases the risk of development, or aggravation, of metabolic syndrome. An increase in both atmospheric pressure and oxygen concentration enhances oxidative enzyme activity in mitochondria and consequently increases oxidative metabolism in cells and tissues. Thus, mild hyperbaric oxygen at 1.25 ATA with 36% oxygen would be expected to improve the decreased oxidative capacity of skeletal muscles and their fibers in rats with metabolic syndrome. In this study, we examined the effects of mild hyperbaric oxygen on the properties of the soleus muscle in rats with metabolic syndrome.
Mild hyperbaric oxygen at 1.25 ATA with 36% oxygen inhibited a growth-related increase in blood glucose levels and decrease in muscle oxidative capacity of rats with metabolic syndrome via improved oxidative metabolism induced by increased blood flow and dissolved oxygen.
Ai Takemura and Akihiko Ishihara Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan, J Atheroscler Thromb, 2017; 24: 26-38. DOI: 10.5551/jat.34686