Effect of exercise training on the density of endothelial cells in the white adipose tissue of rats: Exercise and adipose endothelial cells

We examined the effects of a 9-week exercise training (TR) in Wistar male rats, beginning at 4 weeks of age, on the density of endothelial cells (ECs) in epididymal white adipose tissue (WAT) and the mRNA expression of angiogenic factors in adipose tissue stromal vascular fraction (SVF) cells. The number of ECs and mRNA expressions were assessed by lectin staining and real-time reverse transcriptase-polymerase chain reaction, respectively. Compared with control (CR) rats, TR rats gained weight more slowly and had significantly lower final weight of WAT due to the reduction in the size and the number of adipocytes. TR significantly increased the number of ECs per square millimeter and per adipocyte (1.37- and 1.23-fold, respectively) in WAT. This is probably because the number of adipocytes is fewer while the number of ECs is constant in the WAT of TR rats, because the regression line of TR rats for adipocyte number-dependent EC number was shifted toward the left without significant differences in the slopes between groups. TR also induced the upregulation of mRNA expression of vascular endothelial growth factor (Vegf)-A and Vegf-receptor-2 in SVF cells, thereby retaining a constant number of ECs in the WAT.