Effects of Exercise On Satellite Cell Activity
Satellite cell activation is measured by the extent of proliferation and differentiation. Typically, satellite cell content is expressed per muscle fiber or as a percentage of total nuclear content, the sum of satellite cell nuclei and myonuclei. While the adaptive response to exercise largely varies on an individual basis on factors such as genetics, age, diet, acclimatization to exercise, and exercise volume, human studies have demonstrated general trends.
It is suggested that exercise triggers the release of signaling molecules including inflammatory substances, cytokines and growth factors from surrounding connective tissues and active skeletal muscles. Notably, HGF, a cytokine, is transferred from the extracellular matrix into muscles through the nitric-oxide dependent pathway. It is thought that HGF activates satellite cells, while insulin growth factor-I (IGF-1) and fibroblast growth factor (FGF) enhance satellite cell proliferation rate following activation. Studies have demonstrated that intense exercise generally increases IGF-1 production, though individual responses vary significantly. More specifically, IGF-1 exists in two isoforms: mechano growth factor (MGF) and IGF-IEa. While the former induces activation and proliferation, the latter causes differentiation of proliferating satellite cells.
Human studies have shown that both high resistance training and endurance training have yielded an increased number of satellite cells. These results suggest that a light, endurance training regimen may be useful to counteract the age-correlated satellite cell decrease. In high-resistance training, activation and proliferation of satellite cells are evidenced by increased cyclinD1 mRNA, and p21 mRNA levels. This is consistent with the fact that cyclinD1 and p21 upregulation correlates to division and differentiation of cells.
Satellite cell activation has also been demonstrated on an ultrastructural level following exercise. Aerobic exercise has been shown to significantly increase granular endoplasmic reticulum, free ribosomes, and mitochondria of the stimulated muscle groups. Additionally, satellite cells have been shown to fuse with muscle fibers, developing new muscle fibers. Other ultrastructural evidence for activated satellite cells include increased concentration of Golgi apparatus and pinocytotic vesicles.
Read more about this topic: Myosatellite Cell
Famous quotes containing the words effects of, effects, exercise, satellite, cell and/or activity:
“Trade and commerce, if they were not made of India-rubber, would never manage to bounce over the obstacles which legislators are continually putting in their way; and, if one were to judge these men wholly by the effects of their actions and not partly by their intentions, they would deserve to be classed and punished with those mischievous persons who put obstructions on the railroads.”
—Henry David Thoreau (1817–1862)
“One of the effects of a safe and civilised life is an immense oversensitiveness which makes all the primary emotions somewhat disgusting. Generosity is as painful as meanness, gratitude as hateful as ingratitude.”
—George Orwell (1903–1950)
“The report reflects incredibly terrible judgments, shockingly sparse concern for human life, instances of officials lacking the courage to exercise the responsibilities of their high office and some very bewildering thought processes.”
—Jane Jarrell Smith, U.S. widow of American astronaut Michael J. Smith. As quoted in Newsweek magazine, p. 13 (June 30, 1986)
“Books are the best things, well used; abused, among the worst. What is the right use? What is the one end, which all means go to effect? They are for nothing but to inspire. I had better never see a book, than to be warped by its attraction clean out of my own orbit, and made a satellite instead of a system.”
—Ralph Waldo Emerson (1803–1882)
“What Mrs. Thatcher did for women was to demonstrate that if a woman had enough desire she could do what she wanted, do anything a man could do.... Mrs. Thatcher did not have one traditional feminine cell in her body.”
—Julie Burchill (b. 1960)
“With two sons born eighteen months apart, I operated mainly on automatic pilot through the ceaseless activity of their early childhood. I remember opening the refrigerator late one night and finding a roll of aluminum foil next to a pair of small red tennies. Certain that I was responsible for the refrigerated shoes, I quickly closed the door and ran upstairs to make sure I had put the babies in their cribs instead of the linen closet.”
—Mary Kay Blakely (20th century)