Author:
Xin Dong L,Harris Michelle Y,Wade Christine K,Amin Mamta,Barr Ann E,Barbe Mary F
Abstract
Abstract
Background
We previously reported early tissue injury, increased serum and tissue inflammatory cytokines and decreased grip in young rats performing a moderate demand repetitive task. The tissue cytokine response was transient, the serum response and decreased grip were still evident by 8 weeks. Thus, here, we examined their levels at 12 weeks in young rats. Since aging is known to enhance serum cytokine levels, we also examined aged rats.
Methods
Aged and young rats, 14 mo and 2.5 mo of age at onset, respectfully, were trained 15 min/day for 4 weeks, and then performed a high repetition, low force (HRLF) reaching and grasping task for 2 hours/day, for 12 weeks. Serum was assayed for 6 cytokines: IL-1alpha, IL-6, IFN-gamma, TNF-alpha, MIP2, IL-10. Grip strength was assayed, since we have previously shown an inverse correlation between grip strength and serum inflammatory cytokines. Results were compared to naïve (grip), and normal, food-restricted and trained-only controls.
Results
Serum cytokines were higher overall in aged than young rats, with increases in IL-1alpha, IFN-gamma and IL-6 in aged Trained and 12-week HRLF rats, compared to young Trained and HRLF rats (p < 0.05 and p < 0.001, respectively, each). IL-6 was also increased in aged 12-week HRLF versus aged normal controls (p < 0.05). Serum IFN-gamma and MIP2 levels were also increased in young 6-week HRLF rats, but no cytokines were above baseline levels in young 12-week HRLF rats. Grip strength declined in both young and aged 12-week HRLF rats, compared to naïve and normal controls (p < 0.05 each), but these declines correlated only with IL-6 levels in aged rats (r = -0.39).
Conclusion
Aging enhanced a serum cytokine response in general, a response that was even greater with repetitive task performance. Grip strength was adversely affected by task performance in both age groups, but was apparently influenced by factors other than serum cytokine levels in young rats.
Publisher
Springer Science and Business Media LLC
Subject
Orthopedics and Sports Medicine,Rheumatology
Reference50 articles.
1. Bureau of Labor Statistics: Incidence of nonfatal occupational injuries and illnesses involving days away from work by occupation and selected parts of body affected by injury or illness. 2006, [http://www.bls.gov/iif/oshwc/osh/case/ostb1889.pdf]
2. Bureau of Labor Statistics: Number of nonfatal occupational injuries and illnesses involving days away from work by occupation and selected parts of body affected by injury or illness. 2006, [http://www.bls.gov/iif/oshwc/osh/case/ostb1666.pdf]
3. Ratzlaff CR, Gillies JH, Koehoorn MW: Work-related repetitive strain injury and leisure-time physical activity. Arthritis Rheum. 2007, 57 (3): 495-500. 10.1002/art.22610.
4. Bureau of Labor Statistics: Nonfatal occupational injuries and illnesses requiring days away from work. 2009, [http://www.bls.gov/news.release/osh2.nr0.htm]
5. Gerr F, Marcus M, Ensor C, Kleinbaum D, Cohen S, Edwards A, Gentry E, Ortiz DJ, Monteilh C: A prospective study of computer users: I. Study design and incidence of musculoskeletal symptoms and disorders. Am J Ind Med. 2002, 41 (4): 221-235. 10.1002/ajim.10066.