Exercise-induced capillary density ups insulin sensitivity

(HealthDay)—Exercise training is associated with an increase in skeletal muscle capillary density (CD), which contributes to improvements in glucose metabolism, according to a study published online June 11 in Diabetes.

Steven J. Prior, Ph.D., from the University of Maryland School of Medicine in Baltimore, and colleagues examined whether increases in skeletal muscle CD contribute to exercise-induced improvements in whole-body insulin sensitivity (M/I). Twelve previously sedentary older men and women underwent six months of aerobic exercise training followed by a two-week detraining period.

The researchers found that exercise training correlated with significant increases in maximal oxygen uptake, CD, and M/I (all P < 0.05). There were also increases in insulin activation of glycogen synthase (60 percent), glucose transporter-4 expression (16 percent), and 5' AMP-activated protein kinase-α1 expression (21 percent) with exercise training; after detraining, these reverted to baseline levels. CD and M/I remained elevated after detraining (18 and 15 percent, respectively: P < 0.05). In regression analysis, there was a direct correlation between the changes in M/I with changes in CD.

"These results suggest that an increase in CD is one mechanism contributing to sustained improvements in glucose metabolism after aerobic exercise training," the authors write.

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