Background: Exercise increases blood levels of crucial angiogenic factors and endothelial progenitor cells (EPCs). Hypoxia inducible factor-1 (HIF-1a) and vascular endothelial growth factor (VEGF) are also increased in skeletal muscle in response to exercise. In the healthy heart, voluntary exercise is not expected to cause local hypoxia. We studied how voluntary exercise affects cardiac expression of HIF-1a, VEGF and stromal derived factor-1 (SDF-1), as well as EPC levels in heart and skeletal muscle.
Method: Thirty-two NMRI mice were randomized to exercise in running wheels (EX) or regular activity (SED). HIF-1a, VEGF and SDF-1 mRNA levels were analyzed by reverse transcription polymerase chain reaction (RTPCR) and EPC levels in heart and hind limb were quantified by FACS after 7 and 14 days.
Results: There was no significant difference in cardiac expression of HIF-1a, VEGF or SDF-1 between EX and SED. Cardiac EPC levels were not affected by exercise, while skeletal EPC level was more than doubled.
Conclusion: Voluntary exercise does not seem to induce cardiac hypoxia or stimulate the angiogenic system. In the healthy normoxic heart, there is a limited need of supporting blood supply, which might explain these findings.