Effect of short- and long-term physical activities on circulating granin protein levels

Background: The classic chromogranin-secretogranin (granin) proteins are produced in the myocardium and throughout the neuroendocrine system, but while chromogranin (Cg) A and B levels are high in the adrenal medulla, secretogranin (Sg) II production is higher in the pituitary gland. Whether these differences may influence the response to physical activity is not known.

Methods: We measured circulating granin proteins during (1) a short-term maximal bicycle exercise stress test and (2) a 7 day military ranger course of continuous physical activity and sleep and energy deprivation.

Results: In 9 healthy subjects performing the exercise stress test (7 male, age 45±5 y [mean±SEM], duration 10.13±1.14 min), CgB levels increased from before to immediately after the test: 1.20±0.12 vs. 1.45±0.09 nmol/L, p=0.013. Metabolic equivalents, representing an index of performed work, were closely associated with the change (∆) in CgB levels during stress testing and explained 74% of the variability in ∆CgB levels (p=0.004). CgA and SgII levels were not increased after exercise stress testing. In the second cohort of 8 male subjects (age 25±1 y) participating in the ranger course, CgB levels increased from day 1 and were significantly elevated on days 5 and 7. CgA also increased gradually with levels significantly elevated on day 7, while SgII was markedly increased on day 5 whereas levels on days 3 and 7 were unchanged compared to baseline levels.

Conclusion: We demonstrate a heterogeneous response to short- and long-term physical activities among circulating granin proteins with the most potent effect on CgB levels.