Temporal response of positive and negative regulators in response to acute and chronic exercise training in mice

Abstract

Key points• Angiogenic regulators respond to acute exercise with different temporal expression patterns (e.g. 2-4 h versus 12-24 h) creating a complex multifaceted response that must be considered in studies using a single time point for post-exercise analyses.• In response to chronic training there appears to be a complex coordination in the proteomic responses of both positive and negative angiogenic factors that correspond with training-induced muscle capillary adaptation, such that altered basal expression and acute responses to exercise appear to withdraw or reduce the stimulus of angiogenic regulators in an expanding capillary bed with active angiogenesis.• These are the first data to show that nucleolin (a protein responsible for transcriptional processing and transportation of proteins from the cytoplasm to the nucleus) is responsive to acute exercise. We speculate that nucleolin may work in concert with vascular endothelial growth factor-A (VEGF) and endostatin.• Temporal responses observed in mice, particularly for VEGF, MMP-2 and MMP-9, may not be directly comparable to humans.Abstract Angiogenesis is controlled by a balance between positive and negative angiogenic factors, but temporal protein expression of many key angiogenic regulators in response to exercise are still poorly defined. In C57BL/6 mice, we evaluated the temporal protein expression of several pro-angiogenic and anti-angiogenic factors in response to (1) a single acute bout of exercise and (2) chronic exercise training resulting from 3, 5, 7, 14 and 28 days of voluntary wheel running. Following acute exercise, protein levels of vascular endothelial growth factor-A (VEGF), endostatin and nucleolin were increased at 2-4 h (P < 0.05), whereas matrix metalloproteinase (MMP)-2 was elevated within a 12-24 h window (P < 0.05). Training increased muscle capillarity 11%, 15% and 22% starting with 7, 14 and 28 days of training, respectively (P < 0.01). Basal VEGF and MMP-2 were increased by 31% and 22%, respectively, compared to controls (P < 0.05) after 7 days (7d) training, but decreased to back to baseline after 14d training. After 28d training VEGF fell 49% below baseline control (P < 0.01). Basal muscle expression of thrombospondin 1 (TSP-1) was ∼900% greater in 14d-and 28d-trained mice compared to either 5d-and 7d-trained mice (P < 0.05), and tended to increase by ∼180-258% compared to basal control levels (P < 0.10).The acute responsiveness of VEGF to exercise in untrained mice (i.e. 161% increase, P < 0.001) was lost with capillary adaptation occurring after 7, 14 and 28d training. Taken together, these data support the notion that skeletal muscle angiogenesis is controlled by a balance between positive and negative mitogens, and reveals a complex, highly-coordinated, temporal scheme whereby these factors can differentially influence capillary growth in response to acute versus chronic exercise.

Cardiovascular Adaptations to Exercise Training

“…The discrepancies between studies in humans and animals may largely be related to that earlier time points after onset of training are studied in rodents. A study on the time course of expression of proangiogenic and antiangiogenic compounds in rodents by Olenich and co-workers suggests that VEGF levels are increased within a few days of training and then reduced after 2 to 4 weeks of training (320). This time course is consistent with findings in humans showing an increase in muscle VEGF protein at 10 days of training but similar VEGF protein levels after 4 weeks of training (152).…”

Alpha adrenergic receptor blockade increases capillarization and fractional O2 extraction and lowers blood flow in contracting human skeletal muscle

“…In contrast, levels of eNOS are generally enhanced with aerobic training (Hellsten & Nyberg, 2015), and both acute and repeated passive movement increases expression of eNOS mRNA (Hellsten et al, 2008;Hoier et al, 2010). The response of angiogenic factors in rodent skeletal muscle differ somewhat from what is generally found in humans in that levels of VEGF, VEGF receptor 2, TSP-1 in mice and rats appear to be more readily altered by a period of stimuli such as muscle contraction, shear stress or passive stretch (Williams et al, 2006b;Olenich et al, 2013). This may be linked to the greater stimulus intensity leading to a more rapid angiogenic response in rodents.…”

Transcriptional and Post-Transcriptional Regulation of Thrombospondin-1 Expression: A Computational Model

“…The biology of hypoxia-induced TSP-1 seems contradictory to the need of angiogenesis when cells are exposed to insufficient oxygen, however, this phenomenon may be more likely an endogenous feedback control developed by the body to contain the angiogenesis driven by pro-angiogenic factors (e.g. VEGF) that are radically produced upon hypoxia [140]. …”