Effects of exercise training on adipogenesis of stromal-vascular fraction cells in rat epididymal white adipose tissue

Aim: Previous studies have shown that exercise training reduced white adipose tissue (WAT) mass compared to that in sedentary controls, and that the smaller mass contained fewer adipocytes. However, the effect of exercise training on adipogenesis is not completely clear. Therefore, we re-examined the effect of exercise training on adipocyte numbers in WAT and, if such an effect was found tested the adipogenic responses of stromal-vascular fraction (SVF) cells containing adipose tissue-derived stem cells (ADSC) in epididymal WAT from exercise-trained (TR) rats. Methods: Wistar male rats were divided into two groups: control (C) and TR. The TR rats were subjected to exercise on a treadmill for 9 weeks. SVF cells containing ADSC were separated from epididymal WAT by centrifugation. Expression of adipocyte differentiation-related genes and adipogenesis of SVF cells were examined. Results: In SVF cells of TR rats, the expression of peroxisome proliferator-activated receptor gamma (PPAR gamma) and that of PPAR gamma target lipogenic genes was dramatically downregulated, whereas that of preadipocyte factor-1 gene was significantly upregulated. Lipid accumulation in SVF cells of TR rats after the induction of adipocyte differentiation was significantly suppressed in comparison with that of C rats. Moreover, increased expression of hypoxia-inducible factor-1 alpha (HIF-1 alpha) protein was observed in SVF cells of TR rats. Pre-treatment of YC-1, a potent HIF-1 alpha inhibitor, in SVF cells of TR rats restored adipogenesis. Conclusion: These results suggest that exercise training suppresses the ability of SVF cells to differentiate into adipocytes, and that underlying mechanisms involve the upregulation of HIF-1 alpha expression.