Exercise Training Prevents Decrease in Luminal Capillary Diameter of Skeletal Muscles in Rats with Type 2 Diabetes

Abstract

The purpose of this study was to examine whether exercise training can prevent microangiopathy of skeletal muscles in rats with type 2 diabetes and if succinate dehydrogenase (SDH) activity, an indicator of mitochondrial oxidative enzyme activity, is involved in the prevention of microangiopathy. Six-week-old male Goto-Kakizaki (GK) rats and age-matched male Wistar rats (control group (Con)) were used. GK rats were randomly assigned to nonexercise (DB) and exercise (DBEx) groups. The DBEx group was trained on a treadmill 5 times a week for 3 weeks. No significant differences in the capillary-to-fibre ratio or the capillary density were observed between the 3 groups. The luminal capillary diameter of the DB group was significantly lower than that of the Con group, whereas the capillary diameter of the DBEx group was significantly higher than that of the DB group. In addition, SDH activity was significantly higher in the DBEx group than in the Con and DB groups. Microangiopathy of skeletal muscles in type 2 diabetes was correlated with a decrease in the luminal capillary diameter, which was prevented by exercise training. Thus, the mitochondrial oxidative capacity appears to be involved in the overall mechanism by which exercise prevents microangiopathy.

Low‐intensity running exercise enhances the capillary volume and pro‐angiogenic factors in the soleus muscle of type 2 diabetic rats

“…27,28 Similarly, a reduction in muscle capillary density and diameter in an animal model of type 2 diabetes has been reported. 7,8 Thus, impaired capillarity is observed in skeletal muscles of both type 1 and type 2 diabetic animals. The results of all of these studies, however, were based on 2D capillary staining of muscle cross sections.…”

“…Diabetes has been associated with microvascular complications and impaired angiogenesis in skeletal muscle. 1,[7][8][9][10]26,27 Diabetes-induced remodeling of capillary networks in skeletal muscles results in smaller capillary diameter, lower capillary-to-fiber ratio, and reduced capillary diffusing capacity in animal models of type 1 diabetes. 27,28 Similarly, a reduction in muscle capillary density and diameter in an animal model of type 2 diabetes has been reported.…”

“…Repetitive exercise has also been shown to improve glucose tolerance and/or insulin sensitivity in type 2 diabetic subjects . Moreover, several studies have reported the effects of low‐intensity exercise on capillary density and changes in capillarity in skeletal muscles of diabetic rats . The results of these studies, however, were based on two‐dimensional (2D) analysis of capillarity in skeletal muscle cross sections.…”

“…14 Moreover, several studies have reported the effects of low-intensity exercise on capillary density and changes in capillarity in skeletal muscles of diabetic rats. 8,15 The results of these studies, however, were based on twodimensional (2D) analysis of capillarity in skeletal muscle cross sections. In the present study, we used 3D analysis to visualize structural alterations in the capillary network of skeletal muscles in diabetic rats.…”

Capillary growth and regression in skeletal muscle

“…Skeletal muscle of diabetes has been associated with a reduction in capillary diameter, capillary/fiber ratio, and reduced capillary diffusing capacity in animal models of diabetes 37,38) . In addition, we demonstrated regression of the capillary network in skeletal muscle with diabetes, e.g., decreased diameter, tortuosity and volume, using a three-dimensional visualizing method 7,8,39,40) . Therefore, regression of the capillary network in skeletal muscle caused by diabetes can negatively impact O2 exchange, and consequently may play a role in diabetic complications.…”